Line data Source code
1 : // SPDX-License-Identifier: GPL-2.0
2 : /*
3 : * linux/mm/compaction.c
4 : *
5 : * Memory compaction for the reduction of external fragmentation. Note that
6 : * this heavily depends upon page migration to do all the real heavy
7 : * lifting
8 : *
9 : * Copyright IBM Corp. 2007-2010 Mel Gorman <mel@csn.ul.ie>
10 : */
11 : #include <linux/cpu.h>
12 : #include <linux/swap.h>
13 : #include <linux/migrate.h>
14 : #include <linux/compaction.h>
15 : #include <linux/mm_inline.h>
16 : #include <linux/sched/signal.h>
17 : #include <linux/backing-dev.h>
18 : #include <linux/sysctl.h>
19 : #include <linux/sysfs.h>
20 : #include <linux/page-isolation.h>
21 : #include <linux/kasan.h>
22 : #include <linux/kthread.h>
23 : #include <linux/freezer.h>
24 : #include <linux/page_owner.h>
25 : #include <linux/psi.h>
26 : #include "internal.h"
27 :
28 : #ifdef CONFIG_COMPACTION
29 : /*
30 : * Fragmentation score check interval for proactive compaction purposes.
31 : */
32 : #define HPAGE_FRAG_CHECK_INTERVAL_MSEC (500)
33 :
34 : static inline void count_compact_event(enum vm_event_item item)
35 : {
36 0 : count_vm_event(item);
37 : }
38 :
39 : static inline void count_compact_events(enum vm_event_item item, long delta)
40 : {
41 0 : count_vm_events(item, delta);
42 : }
43 : #else
44 : #define count_compact_event(item) do { } while (0)
45 : #define count_compact_events(item, delta) do { } while (0)
46 : #endif
47 :
48 : #if defined CONFIG_COMPACTION || defined CONFIG_CMA
49 :
50 : #define CREATE_TRACE_POINTS
51 : #include <trace/events/compaction.h>
52 :
53 : #define block_start_pfn(pfn, order) round_down(pfn, 1UL << (order))
54 : #define block_end_pfn(pfn, order) ALIGN((pfn) + 1, 1UL << (order))
55 :
56 : /*
57 : * Page order with-respect-to which proactive compaction
58 : * calculates external fragmentation, which is used as
59 : * the "fragmentation score" of a node/zone.
60 : */
61 : #if defined CONFIG_TRANSPARENT_HUGEPAGE
62 : #define COMPACTION_HPAGE_ORDER HPAGE_PMD_ORDER
63 : #elif defined CONFIG_HUGETLBFS
64 : #define COMPACTION_HPAGE_ORDER HUGETLB_PAGE_ORDER
65 : #else
66 : #define COMPACTION_HPAGE_ORDER (PMD_SHIFT - PAGE_SHIFT)
67 : #endif
68 :
69 0 : static unsigned long release_freepages(struct list_head *freelist)
70 : {
71 : struct page *page, *next;
72 0 : unsigned long high_pfn = 0;
73 :
74 0 : list_for_each_entry_safe(page, next, freelist, lru) {
75 0 : unsigned long pfn = page_to_pfn(page);
76 0 : list_del(&page->lru);
77 0 : __free_page(page);
78 0 : if (pfn > high_pfn)
79 0 : high_pfn = pfn;
80 : }
81 :
82 0 : return high_pfn;
83 : }
84 :
85 0 : static void split_map_pages(struct list_head *list)
86 : {
87 : unsigned int i, order, nr_pages;
88 : struct page *page, *next;
89 0 : LIST_HEAD(tmp_list);
90 :
91 0 : list_for_each_entry_safe(page, next, list, lru) {
92 0 : list_del(&page->lru);
93 :
94 0 : order = page_private(page);
95 0 : nr_pages = 1 << order;
96 :
97 0 : post_alloc_hook(page, order, __GFP_MOVABLE);
98 0 : if (order)
99 0 : split_page(page, order);
100 :
101 0 : for (i = 0; i < nr_pages; i++) {
102 0 : list_add(&page->lru, &tmp_list);
103 0 : page++;
104 : }
105 : }
106 :
107 0 : list_splice(&tmp_list, list);
108 0 : }
109 :
110 : #ifdef CONFIG_COMPACTION
111 0 : bool PageMovable(struct page *page)
112 : {
113 : const struct movable_operations *mops;
114 :
115 : VM_BUG_ON_PAGE(!PageLocked(page), page);
116 0 : if (!__PageMovable(page))
117 : return false;
118 :
119 0 : mops = page_movable_ops(page);
120 0 : if (mops)
121 : return true;
122 :
123 0 : return false;
124 : }
125 :
126 0 : void __SetPageMovable(struct page *page, const struct movable_operations *mops)
127 : {
128 : VM_BUG_ON_PAGE(!PageLocked(page), page);
129 : VM_BUG_ON_PAGE((unsigned long)mops & PAGE_MAPPING_MOVABLE, page);
130 0 : page->mapping = (void *)((unsigned long)mops | PAGE_MAPPING_MOVABLE);
131 0 : }
132 : EXPORT_SYMBOL(__SetPageMovable);
133 :
134 0 : void __ClearPageMovable(struct page *page)
135 : {
136 : VM_BUG_ON_PAGE(!PageMovable(page), page);
137 : /*
138 : * This page still has the type of a movable page, but it's
139 : * actually not movable any more.
140 : */
141 0 : page->mapping = (void *)PAGE_MAPPING_MOVABLE;
142 0 : }
143 : EXPORT_SYMBOL(__ClearPageMovable);
144 :
145 : /* Do not skip compaction more than 64 times */
146 : #define COMPACT_MAX_DEFER_SHIFT 6
147 :
148 : /*
149 : * Compaction is deferred when compaction fails to result in a page
150 : * allocation success. 1 << compact_defer_shift, compactions are skipped up
151 : * to a limit of 1 << COMPACT_MAX_DEFER_SHIFT
152 : */
153 : static void defer_compaction(struct zone *zone, int order)
154 : {
155 0 : zone->compact_considered = 0;
156 0 : zone->compact_defer_shift++;
157 :
158 0 : if (order < zone->compact_order_failed)
159 0 : zone->compact_order_failed = order;
160 :
161 0 : if (zone->compact_defer_shift > COMPACT_MAX_DEFER_SHIFT)
162 0 : zone->compact_defer_shift = COMPACT_MAX_DEFER_SHIFT;
163 :
164 : trace_mm_compaction_defer_compaction(zone, order);
165 : }
166 :
167 : /* Returns true if compaction should be skipped this time */
168 : static bool compaction_deferred(struct zone *zone, int order)
169 : {
170 0 : unsigned long defer_limit = 1UL << zone->compact_defer_shift;
171 :
172 0 : if (order < zone->compact_order_failed)
173 : return false;
174 :
175 : /* Avoid possible overflow */
176 0 : if (++zone->compact_considered >= defer_limit) {
177 0 : zone->compact_considered = defer_limit;
178 : return false;
179 : }
180 :
181 : trace_mm_compaction_deferred(zone, order);
182 :
183 : return true;
184 : }
185 :
186 : /*
187 : * Update defer tracking counters after successful compaction of given order,
188 : * which means an allocation either succeeded (alloc_success == true) or is
189 : * expected to succeed.
190 : */
191 0 : void compaction_defer_reset(struct zone *zone, int order,
192 : bool alloc_success)
193 : {
194 0 : if (alloc_success) {
195 0 : zone->compact_considered = 0;
196 0 : zone->compact_defer_shift = 0;
197 : }
198 0 : if (order >= zone->compact_order_failed)
199 0 : zone->compact_order_failed = order + 1;
200 :
201 0 : trace_mm_compaction_defer_reset(zone, order);
202 0 : }
203 :
204 : /* Returns true if restarting compaction after many failures */
205 : static bool compaction_restarting(struct zone *zone, int order)
206 : {
207 0 : if (order < zone->compact_order_failed)
208 : return false;
209 :
210 0 : return zone->compact_defer_shift == COMPACT_MAX_DEFER_SHIFT &&
211 0 : zone->compact_considered >= 1UL << zone->compact_defer_shift;
212 : }
213 :
214 : /* Returns true if the pageblock should be scanned for pages to isolate. */
215 : static inline bool isolation_suitable(struct compact_control *cc,
216 : struct page *page)
217 : {
218 0 : if (cc->ignore_skip_hint)
219 : return true;
220 :
221 0 : return !get_pageblock_skip(page);
222 : }
223 :
224 : static void reset_cached_positions(struct zone *zone)
225 : {
226 0 : zone->compact_cached_migrate_pfn[0] = zone->zone_start_pfn;
227 0 : zone->compact_cached_migrate_pfn[1] = zone->zone_start_pfn;
228 0 : zone->compact_cached_free_pfn =
229 0 : pageblock_start_pfn(zone_end_pfn(zone) - 1);
230 : }
231 :
232 : /*
233 : * Compound pages of >= pageblock_order should consistently be skipped until
234 : * released. It is always pointless to compact pages of such order (if they are
235 : * migratable), and the pageblocks they occupy cannot contain any free pages.
236 : */
237 0 : static bool pageblock_skip_persistent(struct page *page)
238 : {
239 0 : if (!PageCompound(page))
240 : return false;
241 :
242 0 : page = compound_head(page);
243 :
244 0 : if (compound_order(page) >= pageblock_order)
245 : return true;
246 :
247 0 : return false;
248 : }
249 :
250 : static bool
251 0 : __reset_isolation_pfn(struct zone *zone, unsigned long pfn, bool check_source,
252 : bool check_target)
253 : {
254 0 : struct page *page = pfn_to_online_page(pfn);
255 : struct page *block_page;
256 : struct page *end_page;
257 : unsigned long block_pfn;
258 :
259 0 : if (!page)
260 : return false;
261 0 : if (zone != page_zone(page))
262 : return false;
263 0 : if (pageblock_skip_persistent(page))
264 : return false;
265 :
266 : /*
267 : * If skip is already cleared do no further checking once the
268 : * restart points have been set.
269 : */
270 0 : if (check_source && check_target && !get_pageblock_skip(page))
271 : return true;
272 :
273 : /*
274 : * If clearing skip for the target scanner, do not select a
275 : * non-movable pageblock as the starting point.
276 : */
277 0 : if (!check_source && check_target &&
278 0 : get_pageblock_migratetype(page) != MIGRATE_MOVABLE)
279 : return false;
280 :
281 : /* Ensure the start of the pageblock or zone is online and valid */
282 0 : block_pfn = pageblock_start_pfn(pfn);
283 0 : block_pfn = max(block_pfn, zone->zone_start_pfn);
284 0 : block_page = pfn_to_online_page(block_pfn);
285 0 : if (block_page) {
286 0 : page = block_page;
287 0 : pfn = block_pfn;
288 : }
289 :
290 : /* Ensure the end of the pageblock or zone is online and valid */
291 0 : block_pfn = pageblock_end_pfn(pfn) - 1;
292 0 : block_pfn = min(block_pfn, zone_end_pfn(zone) - 1);
293 0 : end_page = pfn_to_online_page(block_pfn);
294 0 : if (!end_page)
295 : return false;
296 :
297 : /*
298 : * Only clear the hint if a sample indicates there is either a
299 : * free page or an LRU page in the block. One or other condition
300 : * is necessary for the block to be a migration source/target.
301 : */
302 : do {
303 0 : if (check_source && PageLRU(page)) {
304 0 : clear_pageblock_skip(page);
305 0 : return true;
306 : }
307 :
308 0 : if (check_target && PageBuddy(page)) {
309 0 : clear_pageblock_skip(page);
310 0 : return true;
311 : }
312 :
313 0 : page += (1 << PAGE_ALLOC_COSTLY_ORDER);
314 0 : } while (page <= end_page);
315 :
316 : return false;
317 : }
318 :
319 : /*
320 : * This function is called to clear all cached information on pageblocks that
321 : * should be skipped for page isolation when the migrate and free page scanner
322 : * meet.
323 : */
324 0 : static void __reset_isolation_suitable(struct zone *zone)
325 : {
326 0 : unsigned long migrate_pfn = zone->zone_start_pfn;
327 0 : unsigned long free_pfn = zone_end_pfn(zone) - 1;
328 0 : unsigned long reset_migrate = free_pfn;
329 0 : unsigned long reset_free = migrate_pfn;
330 0 : bool source_set = false;
331 0 : bool free_set = false;
332 :
333 0 : if (!zone->compact_blockskip_flush)
334 : return;
335 :
336 0 : zone->compact_blockskip_flush = false;
337 :
338 : /*
339 : * Walk the zone and update pageblock skip information. Source looks
340 : * for PageLRU while target looks for PageBuddy. When the scanner
341 : * is found, both PageBuddy and PageLRU are checked as the pageblock
342 : * is suitable as both source and target.
343 : */
344 0 : for (; migrate_pfn < free_pfn; migrate_pfn += pageblock_nr_pages,
345 0 : free_pfn -= pageblock_nr_pages) {
346 0 : cond_resched();
347 :
348 : /* Update the migrate PFN */
349 0 : if (__reset_isolation_pfn(zone, migrate_pfn, true, source_set) &&
350 : migrate_pfn < reset_migrate) {
351 0 : source_set = true;
352 0 : reset_migrate = migrate_pfn;
353 0 : zone->compact_init_migrate_pfn = reset_migrate;
354 0 : zone->compact_cached_migrate_pfn[0] = reset_migrate;
355 0 : zone->compact_cached_migrate_pfn[1] = reset_migrate;
356 : }
357 :
358 : /* Update the free PFN */
359 0 : if (__reset_isolation_pfn(zone, free_pfn, free_set, true) &&
360 : free_pfn > reset_free) {
361 0 : free_set = true;
362 0 : reset_free = free_pfn;
363 0 : zone->compact_init_free_pfn = reset_free;
364 0 : zone->compact_cached_free_pfn = reset_free;
365 : }
366 : }
367 :
368 : /* Leave no distance if no suitable block was reset */
369 0 : if (reset_migrate >= reset_free) {
370 0 : zone->compact_cached_migrate_pfn[0] = migrate_pfn;
371 0 : zone->compact_cached_migrate_pfn[1] = migrate_pfn;
372 0 : zone->compact_cached_free_pfn = free_pfn;
373 : }
374 : }
375 :
376 1 : void reset_isolation_suitable(pg_data_t *pgdat)
377 : {
378 : int zoneid;
379 :
380 3 : for (zoneid = 0; zoneid < MAX_NR_ZONES; zoneid++) {
381 2 : struct zone *zone = &pgdat->node_zones[zoneid];
382 2 : if (!populated_zone(zone))
383 1 : continue;
384 :
385 : /* Only flush if a full compaction finished recently */
386 1 : if (zone->compact_blockskip_flush)
387 0 : __reset_isolation_suitable(zone);
388 : }
389 1 : }
390 :
391 : /*
392 : * Sets the pageblock skip bit if it was clear. Note that this is a hint as
393 : * locks are not required for read/writers. Returns true if it was already set.
394 : */
395 0 : static bool test_and_set_skip(struct compact_control *cc, struct page *page,
396 : unsigned long pfn)
397 : {
398 : bool skip;
399 :
400 : /* Do no update if skip hint is being ignored */
401 0 : if (cc->ignore_skip_hint)
402 : return false;
403 :
404 0 : if (!pageblock_aligned(pfn))
405 : return false;
406 :
407 0 : skip = get_pageblock_skip(page);
408 0 : if (!skip && !cc->no_set_skip_hint)
409 0 : set_pageblock_skip(page);
410 :
411 : return skip;
412 : }
413 :
414 : static void update_cached_migrate(struct compact_control *cc, unsigned long pfn)
415 : {
416 0 : struct zone *zone = cc->zone;
417 :
418 0 : pfn = pageblock_end_pfn(pfn);
419 :
420 : /* Set for isolation rather than compaction */
421 0 : if (cc->no_set_skip_hint)
422 : return;
423 :
424 0 : if (pfn > zone->compact_cached_migrate_pfn[0])
425 0 : zone->compact_cached_migrate_pfn[0] = pfn;
426 0 : if (cc->mode != MIGRATE_ASYNC &&
427 0 : pfn > zone->compact_cached_migrate_pfn[1])
428 0 : zone->compact_cached_migrate_pfn[1] = pfn;
429 : }
430 :
431 : /*
432 : * If no pages were isolated then mark this pageblock to be skipped in the
433 : * future. The information is later cleared by __reset_isolation_suitable().
434 : */
435 0 : static void update_pageblock_skip(struct compact_control *cc,
436 : struct page *page, unsigned long pfn)
437 : {
438 0 : struct zone *zone = cc->zone;
439 :
440 0 : if (cc->no_set_skip_hint)
441 : return;
442 :
443 0 : if (!page)
444 : return;
445 :
446 0 : set_pageblock_skip(page);
447 :
448 : /* Update where async and sync compaction should restart */
449 0 : if (pfn < zone->compact_cached_free_pfn)
450 0 : zone->compact_cached_free_pfn = pfn;
451 : }
452 : #else
453 : static inline bool isolation_suitable(struct compact_control *cc,
454 : struct page *page)
455 : {
456 : return true;
457 : }
458 :
459 : static inline bool pageblock_skip_persistent(struct page *page)
460 : {
461 : return false;
462 : }
463 :
464 : static inline void update_pageblock_skip(struct compact_control *cc,
465 : struct page *page, unsigned long pfn)
466 : {
467 : }
468 :
469 : static void update_cached_migrate(struct compact_control *cc, unsigned long pfn)
470 : {
471 : }
472 :
473 : static bool test_and_set_skip(struct compact_control *cc, struct page *page,
474 : unsigned long pfn)
475 : {
476 : return false;
477 : }
478 : #endif /* CONFIG_COMPACTION */
479 :
480 : /*
481 : * Compaction requires the taking of some coarse locks that are potentially
482 : * very heavily contended. For async compaction, trylock and record if the
483 : * lock is contended. The lock will still be acquired but compaction will
484 : * abort when the current block is finished regardless of success rate.
485 : * Sync compaction acquires the lock.
486 : *
487 : * Always returns true which makes it easier to track lock state in callers.
488 : */
489 0 : static bool compact_lock_irqsave(spinlock_t *lock, unsigned long *flags,
490 : struct compact_control *cc)
491 : __acquires(lock)
492 : {
493 : /* Track if the lock is contended in async mode */
494 0 : if (cc->mode == MIGRATE_ASYNC && !cc->contended) {
495 0 : if (spin_trylock_irqsave(lock, *flags))
496 : return true;
497 :
498 : cc->contended = true;
499 : }
500 :
501 0 : spin_lock_irqsave(lock, *flags);
502 : return true;
503 : }
504 :
505 : /*
506 : * Compaction requires the taking of some coarse locks that are potentially
507 : * very heavily contended. The lock should be periodically unlocked to avoid
508 : * having disabled IRQs for a long time, even when there is nobody waiting on
509 : * the lock. It might also be that allowing the IRQs will result in
510 : * need_resched() becoming true. If scheduling is needed, compaction schedules.
511 : * Either compaction type will also abort if a fatal signal is pending.
512 : * In either case if the lock was locked, it is dropped and not regained.
513 : *
514 : * Returns true if compaction should abort due to fatal signal pending.
515 : * Returns false when compaction can continue.
516 : */
517 0 : static bool compact_unlock_should_abort(spinlock_t *lock,
518 : unsigned long flags, bool *locked, struct compact_control *cc)
519 : {
520 0 : if (*locked) {
521 0 : spin_unlock_irqrestore(lock, flags);
522 0 : *locked = false;
523 : }
524 :
525 0 : if (fatal_signal_pending(current)) {
526 0 : cc->contended = true;
527 : return true;
528 : }
529 :
530 0 : cond_resched();
531 :
532 : return false;
533 : }
534 :
535 : /*
536 : * Isolate free pages onto a private freelist. If @strict is true, will abort
537 : * returning 0 on any invalid PFNs or non-free pages inside of the pageblock
538 : * (even though it may still end up isolating some pages).
539 : */
540 0 : static unsigned long isolate_freepages_block(struct compact_control *cc,
541 : unsigned long *start_pfn,
542 : unsigned long end_pfn,
543 : struct list_head *freelist,
544 : unsigned int stride,
545 : bool strict)
546 : {
547 0 : int nr_scanned = 0, total_isolated = 0;
548 : struct page *cursor;
549 0 : unsigned long flags = 0;
550 0 : bool locked = false;
551 0 : unsigned long blockpfn = *start_pfn;
552 : unsigned int order;
553 :
554 : /* Strict mode is for isolation, speed is secondary */
555 0 : if (strict)
556 0 : stride = 1;
557 :
558 0 : cursor = pfn_to_page(blockpfn);
559 :
560 : /* Isolate free pages. */
561 0 : for (; blockpfn < end_pfn; blockpfn += stride, cursor += stride) {
562 : int isolated;
563 0 : struct page *page = cursor;
564 :
565 : /*
566 : * Periodically drop the lock (if held) regardless of its
567 : * contention, to give chance to IRQs. Abort if fatal signal
568 : * pending.
569 : */
570 0 : if (!(blockpfn % COMPACT_CLUSTER_MAX)
571 0 : && compact_unlock_should_abort(&cc->zone->lock, flags,
572 : &locked, cc))
573 : break;
574 :
575 0 : nr_scanned++;
576 :
577 : /*
578 : * For compound pages such as THP and hugetlbfs, we can save
579 : * potentially a lot of iterations if we skip them at once.
580 : * The check is racy, but we can consider only valid values
581 : * and the only danger is skipping too much.
582 : */
583 0 : if (PageCompound(page)) {
584 0 : const unsigned int order = compound_order(page);
585 :
586 0 : if (likely(order < MAX_ORDER)) {
587 0 : blockpfn += (1UL << order) - 1;
588 0 : cursor += (1UL << order) - 1;
589 : }
590 : goto isolate_fail;
591 : }
592 :
593 0 : if (!PageBuddy(page))
594 : goto isolate_fail;
595 :
596 : /* If we already hold the lock, we can skip some rechecking. */
597 0 : if (!locked) {
598 0 : locked = compact_lock_irqsave(&cc->zone->lock,
599 : &flags, cc);
600 :
601 : /* Recheck this is a buddy page under lock */
602 0 : if (!PageBuddy(page))
603 : goto isolate_fail;
604 : }
605 :
606 : /* Found a free page, will break it into order-0 pages */
607 0 : order = buddy_order(page);
608 0 : isolated = __isolate_free_page(page, order);
609 0 : if (!isolated)
610 : break;
611 0 : set_page_private(page, order);
612 :
613 0 : nr_scanned += isolated - 1;
614 0 : total_isolated += isolated;
615 0 : cc->nr_freepages += isolated;
616 0 : list_add_tail(&page->lru, freelist);
617 :
618 0 : if (!strict && cc->nr_migratepages <= cc->nr_freepages) {
619 0 : blockpfn += isolated;
620 0 : break;
621 : }
622 : /* Advance to the end of split page */
623 0 : blockpfn += isolated - 1;
624 0 : cursor += isolated - 1;
625 0 : continue;
626 :
627 : isolate_fail:
628 0 : if (strict)
629 : break;
630 : else
631 0 : continue;
632 :
633 : }
634 :
635 0 : if (locked)
636 0 : spin_unlock_irqrestore(&cc->zone->lock, flags);
637 :
638 : /*
639 : * There is a tiny chance that we have read bogus compound_order(),
640 : * so be careful to not go outside of the pageblock.
641 : */
642 0 : if (unlikely(blockpfn > end_pfn))
643 0 : blockpfn = end_pfn;
644 :
645 0 : trace_mm_compaction_isolate_freepages(*start_pfn, blockpfn,
646 : nr_scanned, total_isolated);
647 :
648 : /* Record how far we have got within the block */
649 0 : *start_pfn = blockpfn;
650 :
651 : /*
652 : * If strict isolation is requested by CMA then check that all the
653 : * pages requested were isolated. If there were any failures, 0 is
654 : * returned and CMA will fail.
655 : */
656 0 : if (strict && blockpfn < end_pfn)
657 0 : total_isolated = 0;
658 :
659 0 : cc->total_free_scanned += nr_scanned;
660 0 : if (total_isolated)
661 0 : count_compact_events(COMPACTISOLATED, total_isolated);
662 0 : return total_isolated;
663 : }
664 :
665 : /**
666 : * isolate_freepages_range() - isolate free pages.
667 : * @cc: Compaction control structure.
668 : * @start_pfn: The first PFN to start isolating.
669 : * @end_pfn: The one-past-last PFN.
670 : *
671 : * Non-free pages, invalid PFNs, or zone boundaries within the
672 : * [start_pfn, end_pfn) range are considered errors, cause function to
673 : * undo its actions and return zero.
674 : *
675 : * Otherwise, function returns one-past-the-last PFN of isolated page
676 : * (which may be greater then end_pfn if end fell in a middle of
677 : * a free page).
678 : */
679 : unsigned long
680 0 : isolate_freepages_range(struct compact_control *cc,
681 : unsigned long start_pfn, unsigned long end_pfn)
682 : {
683 : unsigned long isolated, pfn, block_start_pfn, block_end_pfn;
684 0 : LIST_HEAD(freelist);
685 :
686 0 : pfn = start_pfn;
687 0 : block_start_pfn = pageblock_start_pfn(pfn);
688 0 : if (block_start_pfn < cc->zone->zone_start_pfn)
689 0 : block_start_pfn = cc->zone->zone_start_pfn;
690 0 : block_end_pfn = pageblock_end_pfn(pfn);
691 :
692 0 : for (; pfn < end_pfn; pfn += isolated,
693 0 : block_start_pfn = block_end_pfn,
694 0 : block_end_pfn += pageblock_nr_pages) {
695 : /* Protect pfn from changing by isolate_freepages_block */
696 0 : unsigned long isolate_start_pfn = pfn;
697 :
698 0 : block_end_pfn = min(block_end_pfn, end_pfn);
699 :
700 : /*
701 : * pfn could pass the block_end_pfn if isolated freepage
702 : * is more than pageblock order. In this case, we adjust
703 : * scanning range to right one.
704 : */
705 0 : if (pfn >= block_end_pfn) {
706 0 : block_start_pfn = pageblock_start_pfn(pfn);
707 0 : block_end_pfn = pageblock_end_pfn(pfn);
708 0 : block_end_pfn = min(block_end_pfn, end_pfn);
709 : }
710 :
711 0 : if (!pageblock_pfn_to_page(block_start_pfn,
712 : block_end_pfn, cc->zone))
713 : break;
714 :
715 0 : isolated = isolate_freepages_block(cc, &isolate_start_pfn,
716 : block_end_pfn, &freelist, 0, true);
717 :
718 : /*
719 : * In strict mode, isolate_freepages_block() returns 0 if
720 : * there are any holes in the block (ie. invalid PFNs or
721 : * non-free pages).
722 : */
723 0 : if (!isolated)
724 : break;
725 :
726 : /*
727 : * If we managed to isolate pages, it is always (1 << n) *
728 : * pageblock_nr_pages for some non-negative n. (Max order
729 : * page may span two pageblocks).
730 : */
731 : }
732 :
733 : /* __isolate_free_page() does not map the pages */
734 0 : split_map_pages(&freelist);
735 :
736 0 : if (pfn < end_pfn) {
737 : /* Loop terminated early, cleanup. */
738 0 : release_freepages(&freelist);
739 0 : return 0;
740 : }
741 :
742 : /* We don't use freelists for anything. */
743 : return pfn;
744 : }
745 :
746 : /* Similar to reclaim, but different enough that they don't share logic */
747 0 : static bool too_many_isolated(pg_data_t *pgdat)
748 : {
749 : bool too_many;
750 :
751 : unsigned long active, inactive, isolated;
752 :
753 0 : inactive = node_page_state(pgdat, NR_INACTIVE_FILE) +
754 0 : node_page_state(pgdat, NR_INACTIVE_ANON);
755 0 : active = node_page_state(pgdat, NR_ACTIVE_FILE) +
756 0 : node_page_state(pgdat, NR_ACTIVE_ANON);
757 0 : isolated = node_page_state(pgdat, NR_ISOLATED_FILE) +
758 0 : node_page_state(pgdat, NR_ISOLATED_ANON);
759 :
760 0 : too_many = isolated > (inactive + active) / 2;
761 0 : if (!too_many)
762 : wake_throttle_isolated(pgdat);
763 :
764 0 : return too_many;
765 : }
766 :
767 : /**
768 : * isolate_migratepages_block() - isolate all migrate-able pages within
769 : * a single pageblock
770 : * @cc: Compaction control structure.
771 : * @low_pfn: The first PFN to isolate
772 : * @end_pfn: The one-past-the-last PFN to isolate, within same pageblock
773 : * @mode: Isolation mode to be used.
774 : *
775 : * Isolate all pages that can be migrated from the range specified by
776 : * [low_pfn, end_pfn). The range is expected to be within same pageblock.
777 : * Returns errno, like -EAGAIN or -EINTR in case e.g signal pending or congestion,
778 : * -ENOMEM in case we could not allocate a page, or 0.
779 : * cc->migrate_pfn will contain the next pfn to scan.
780 : *
781 : * The pages are isolated on cc->migratepages list (not required to be empty),
782 : * and cc->nr_migratepages is updated accordingly.
783 : */
784 : static int
785 0 : isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
786 : unsigned long end_pfn, isolate_mode_t mode)
787 : {
788 0 : pg_data_t *pgdat = cc->zone->zone_pgdat;
789 0 : unsigned long nr_scanned = 0, nr_isolated = 0;
790 : struct lruvec *lruvec;
791 0 : unsigned long flags = 0;
792 0 : struct lruvec *locked = NULL;
793 0 : struct page *page = NULL, *valid_page = NULL;
794 : struct address_space *mapping;
795 0 : unsigned long start_pfn = low_pfn;
796 0 : bool skip_on_failure = false;
797 0 : unsigned long next_skip_pfn = 0;
798 0 : bool skip_updated = false;
799 0 : int ret = 0;
800 :
801 0 : cc->migrate_pfn = low_pfn;
802 :
803 : /*
804 : * Ensure that there are not too many pages isolated from the LRU
805 : * list by either parallel reclaimers or compaction. If there are,
806 : * delay for some time until fewer pages are isolated
807 : */
808 0 : while (unlikely(too_many_isolated(pgdat))) {
809 : /* stop isolation if there are still pages not migrated */
810 0 : if (cc->nr_migratepages)
811 : return -EAGAIN;
812 :
813 : /* async migration should just abort */
814 0 : if (cc->mode == MIGRATE_ASYNC)
815 : return -EAGAIN;
816 :
817 0 : reclaim_throttle(pgdat, VMSCAN_THROTTLE_ISOLATED);
818 :
819 0 : if (fatal_signal_pending(current))
820 : return -EINTR;
821 : }
822 :
823 0 : cond_resched();
824 :
825 0 : if (cc->direct_compaction && (cc->mode == MIGRATE_ASYNC)) {
826 0 : skip_on_failure = true;
827 0 : next_skip_pfn = block_end_pfn(low_pfn, cc->order);
828 : }
829 :
830 : /* Time to isolate some pages for migration */
831 0 : for (; low_pfn < end_pfn; low_pfn++) {
832 :
833 0 : if (skip_on_failure && low_pfn >= next_skip_pfn) {
834 : /*
835 : * We have isolated all migration candidates in the
836 : * previous order-aligned block, and did not skip it due
837 : * to failure. We should migrate the pages now and
838 : * hopefully succeed compaction.
839 : */
840 0 : if (nr_isolated)
841 : break;
842 :
843 : /*
844 : * We failed to isolate in the previous order-aligned
845 : * block. Set the new boundary to the end of the
846 : * current block. Note we can't simply increase
847 : * next_skip_pfn by 1 << order, as low_pfn might have
848 : * been incremented by a higher number due to skipping
849 : * a compound or a high-order buddy page in the
850 : * previous loop iteration.
851 : */
852 0 : next_skip_pfn = block_end_pfn(low_pfn, cc->order);
853 : }
854 :
855 : /*
856 : * Periodically drop the lock (if held) regardless of its
857 : * contention, to give chance to IRQs. Abort completely if
858 : * a fatal signal is pending.
859 : */
860 0 : if (!(low_pfn % COMPACT_CLUSTER_MAX)) {
861 0 : if (locked) {
862 0 : unlock_page_lruvec_irqrestore(locked, flags);
863 0 : locked = NULL;
864 : }
865 :
866 0 : if (fatal_signal_pending(current)) {
867 0 : cc->contended = true;
868 0 : ret = -EINTR;
869 :
870 0 : goto fatal_pending;
871 : }
872 :
873 0 : cond_resched();
874 : }
875 :
876 0 : nr_scanned++;
877 :
878 0 : page = pfn_to_page(low_pfn);
879 :
880 : /*
881 : * Check if the pageblock has already been marked skipped.
882 : * Only the aligned PFN is checked as the caller isolates
883 : * COMPACT_CLUSTER_MAX at a time so the second call must
884 : * not falsely conclude that the block should be skipped.
885 : */
886 0 : if (!valid_page && pageblock_aligned(low_pfn)) {
887 0 : if (!isolation_suitable(cc, page)) {
888 : low_pfn = end_pfn;
889 : page = NULL;
890 : goto isolate_abort;
891 : }
892 : valid_page = page;
893 : }
894 :
895 0 : if (PageHuge(page) && cc->alloc_contig) {
896 : ret = isolate_or_dissolve_huge_page(page, &cc->migratepages);
897 :
898 : /*
899 : * Fail isolation in case isolate_or_dissolve_huge_page()
900 : * reports an error. In case of -ENOMEM, abort right away.
901 : */
902 : if (ret < 0) {
903 : /* Do not report -EBUSY down the chain */
904 : if (ret == -EBUSY)
905 : ret = 0;
906 : low_pfn += compound_nr(page) - 1;
907 : goto isolate_fail;
908 : }
909 :
910 : if (PageHuge(page)) {
911 : /*
912 : * Hugepage was successfully isolated and placed
913 : * on the cc->migratepages list.
914 : */
915 : low_pfn += compound_nr(page) - 1;
916 : goto isolate_success_no_list;
917 : }
918 :
919 : /*
920 : * Ok, the hugepage was dissolved. Now these pages are
921 : * Buddy and cannot be re-allocated because they are
922 : * isolated. Fall-through as the check below handles
923 : * Buddy pages.
924 : */
925 : }
926 :
927 : /*
928 : * Skip if free. We read page order here without zone lock
929 : * which is generally unsafe, but the race window is small and
930 : * the worst thing that can happen is that we skip some
931 : * potential isolation targets.
932 : */
933 0 : if (PageBuddy(page)) {
934 0 : unsigned long freepage_order = buddy_order_unsafe(page);
935 :
936 : /*
937 : * Without lock, we cannot be sure that what we got is
938 : * a valid page order. Consider only values in the
939 : * valid order range to prevent low_pfn overflow.
940 : */
941 0 : if (freepage_order > 0 && freepage_order < MAX_ORDER)
942 0 : low_pfn += (1UL << freepage_order) - 1;
943 0 : continue;
944 : }
945 :
946 : /*
947 : * Regardless of being on LRU, compound pages such as THP and
948 : * hugetlbfs are not to be compacted unless we are attempting
949 : * an allocation much larger than the huge page size (eg CMA).
950 : * We can potentially save a lot of iterations if we skip them
951 : * at once. The check is racy, but we can consider only valid
952 : * values and the only danger is skipping too much.
953 : */
954 0 : if (PageCompound(page) && !cc->alloc_contig) {
955 0 : const unsigned int order = compound_order(page);
956 :
957 0 : if (likely(order < MAX_ORDER))
958 0 : low_pfn += (1UL << order) - 1;
959 : goto isolate_fail;
960 : }
961 :
962 : /*
963 : * Check may be lockless but that's ok as we recheck later.
964 : * It's possible to migrate LRU and non-lru movable pages.
965 : * Skip any other type of page
966 : */
967 0 : if (!PageLRU(page)) {
968 : /*
969 : * __PageMovable can return false positive so we need
970 : * to verify it under page_lock.
971 : */
972 0 : if (unlikely(__PageMovable(page)) &&
973 0 : !PageIsolated(page)) {
974 0 : if (locked) {
975 0 : unlock_page_lruvec_irqrestore(locked, flags);
976 0 : locked = NULL;
977 : }
978 :
979 0 : if (isolate_movable_page(page, mode))
980 : goto isolate_success;
981 : }
982 :
983 : goto isolate_fail;
984 : }
985 :
986 : /*
987 : * Be careful not to clear PageLRU until after we're
988 : * sure the page is not being freed elsewhere -- the
989 : * page release code relies on it.
990 : */
991 0 : if (unlikely(!get_page_unless_zero(page)))
992 : goto isolate_fail;
993 :
994 : /*
995 : * Migration will fail if an anonymous page is pinned in memory,
996 : * so avoid taking lru_lock and isolating it unnecessarily in an
997 : * admittedly racy check.
998 : */
999 0 : mapping = page_mapping(page);
1000 0 : if (!mapping && (page_count(page) - 1) > total_mapcount(page))
1001 : goto isolate_fail_put;
1002 :
1003 : /*
1004 : * Only allow to migrate anonymous pages in GFP_NOFS context
1005 : * because those do not depend on fs locks.
1006 : */
1007 0 : if (!(cc->gfp_mask & __GFP_FS) && mapping)
1008 : goto isolate_fail_put;
1009 :
1010 : /* Only take pages on LRU: a check now makes later tests safe */
1011 0 : if (!PageLRU(page))
1012 : goto isolate_fail_put;
1013 :
1014 : /* Compaction might skip unevictable pages but CMA takes them */
1015 0 : if (!(mode & ISOLATE_UNEVICTABLE) && PageUnevictable(page))
1016 : goto isolate_fail_put;
1017 :
1018 : /*
1019 : * To minimise LRU disruption, the caller can indicate with
1020 : * ISOLATE_ASYNC_MIGRATE that it only wants to isolate pages
1021 : * it will be able to migrate without blocking - clean pages
1022 : * for the most part. PageWriteback would require blocking.
1023 : */
1024 0 : if ((mode & ISOLATE_ASYNC_MIGRATE) && PageWriteback(page))
1025 : goto isolate_fail_put;
1026 :
1027 0 : if ((mode & ISOLATE_ASYNC_MIGRATE) && PageDirty(page)) {
1028 : bool migrate_dirty;
1029 :
1030 : /*
1031 : * Only pages without mappings or that have a
1032 : * ->migrate_folio callback are possible to migrate
1033 : * without blocking. However, we can be racing with
1034 : * truncation so it's necessary to lock the page
1035 : * to stabilise the mapping as truncation holds
1036 : * the page lock until after the page is removed
1037 : * from the page cache.
1038 : */
1039 0 : if (!trylock_page(page))
1040 : goto isolate_fail_put;
1041 :
1042 0 : mapping = page_mapping(page);
1043 0 : migrate_dirty = !mapping ||
1044 0 : mapping->a_ops->migrate_folio;
1045 0 : unlock_page(page);
1046 0 : if (!migrate_dirty)
1047 : goto isolate_fail_put;
1048 : }
1049 :
1050 : /* Try isolate the page */
1051 0 : if (!TestClearPageLRU(page))
1052 : goto isolate_fail_put;
1053 :
1054 0 : lruvec = folio_lruvec(page_folio(page));
1055 :
1056 : /* If we already hold the lock, we can skip some rechecking */
1057 0 : if (lruvec != locked) {
1058 0 : if (locked)
1059 0 : unlock_page_lruvec_irqrestore(locked, flags);
1060 :
1061 0 : compact_lock_irqsave(&lruvec->lru_lock, &flags, cc);
1062 0 : locked = lruvec;
1063 :
1064 0 : lruvec_memcg_debug(lruvec, page_folio(page));
1065 :
1066 : /* Try get exclusive access under lock */
1067 0 : if (!skip_updated) {
1068 0 : skip_updated = true;
1069 0 : if (test_and_set_skip(cc, page, low_pfn))
1070 : goto isolate_abort;
1071 : }
1072 :
1073 : /*
1074 : * Page become compound since the non-locked check,
1075 : * and it's on LRU. It can only be a THP so the order
1076 : * is safe to read and it's 0 for tail pages.
1077 : */
1078 0 : if (unlikely(PageCompound(page) && !cc->alloc_contig)) {
1079 0 : low_pfn += compound_nr(page) - 1;
1080 : SetPageLRU(page);
1081 : goto isolate_fail_put;
1082 : }
1083 : }
1084 :
1085 : /* The whole page is taken off the LRU; skip the tail pages. */
1086 0 : if (PageCompound(page))
1087 0 : low_pfn += compound_nr(page) - 1;
1088 :
1089 : /* Successfully isolated */
1090 0 : del_page_from_lru_list(page, lruvec);
1091 0 : mod_node_page_state(page_pgdat(page),
1092 0 : NR_ISOLATED_ANON + page_is_file_lru(page),
1093 : thp_nr_pages(page));
1094 :
1095 : isolate_success:
1096 0 : list_add(&page->lru, &cc->migratepages);
1097 : isolate_success_no_list:
1098 0 : cc->nr_migratepages += compound_nr(page);
1099 0 : nr_isolated += compound_nr(page);
1100 0 : nr_scanned += compound_nr(page) - 1;
1101 :
1102 : /*
1103 : * Avoid isolating too much unless this block is being
1104 : * fully scanned (e.g. dirty/writeback pages, parallel allocation)
1105 : * or a lock is contended. For contention, isolate quickly to
1106 : * potentially remove one source of contention.
1107 : */
1108 0 : if (cc->nr_migratepages >= COMPACT_CLUSTER_MAX &&
1109 0 : !cc->finish_pageblock && !cc->contended) {
1110 0 : ++low_pfn;
1111 0 : break;
1112 : }
1113 :
1114 0 : continue;
1115 :
1116 : isolate_fail_put:
1117 : /* Avoid potential deadlock in freeing page under lru_lock */
1118 0 : if (locked) {
1119 0 : unlock_page_lruvec_irqrestore(locked, flags);
1120 0 : locked = NULL;
1121 : }
1122 0 : put_page(page);
1123 :
1124 : isolate_fail:
1125 0 : if (!skip_on_failure && ret != -ENOMEM)
1126 0 : continue;
1127 :
1128 : /*
1129 : * We have isolated some pages, but then failed. Release them
1130 : * instead of migrating, as we cannot form the cc->order buddy
1131 : * page anyway.
1132 : */
1133 0 : if (nr_isolated) {
1134 0 : if (locked) {
1135 0 : unlock_page_lruvec_irqrestore(locked, flags);
1136 0 : locked = NULL;
1137 : }
1138 0 : putback_movable_pages(&cc->migratepages);
1139 0 : cc->nr_migratepages = 0;
1140 0 : nr_isolated = 0;
1141 : }
1142 :
1143 0 : if (low_pfn < next_skip_pfn) {
1144 0 : low_pfn = next_skip_pfn - 1;
1145 : /*
1146 : * The check near the loop beginning would have updated
1147 : * next_skip_pfn too, but this is a bit simpler.
1148 : */
1149 0 : next_skip_pfn += 1UL << cc->order;
1150 : }
1151 :
1152 : if (ret == -ENOMEM)
1153 : break;
1154 : }
1155 :
1156 : /*
1157 : * The PageBuddy() check could have potentially brought us outside
1158 : * the range to be scanned.
1159 : */
1160 0 : if (unlikely(low_pfn > end_pfn))
1161 0 : low_pfn = end_pfn;
1162 :
1163 : page = NULL;
1164 :
1165 : isolate_abort:
1166 0 : if (locked)
1167 0 : unlock_page_lruvec_irqrestore(locked, flags);
1168 0 : if (page) {
1169 0 : SetPageLRU(page);
1170 0 : put_page(page);
1171 : }
1172 :
1173 : /*
1174 : * Update the cached scanner pfn once the pageblock has been scanned.
1175 : * Pages will either be migrated in which case there is no point
1176 : * scanning in the near future or migration failed in which case the
1177 : * failure reason may persist. The block is marked for skipping if
1178 : * there were no pages isolated in the block or if the block is
1179 : * rescanned twice in a row.
1180 : */
1181 0 : if (low_pfn == end_pfn && (!nr_isolated || cc->finish_pageblock)) {
1182 0 : if (valid_page && !skip_updated)
1183 0 : set_pageblock_skip(valid_page);
1184 : update_cached_migrate(cc, low_pfn);
1185 : }
1186 :
1187 : trace_mm_compaction_isolate_migratepages(start_pfn, low_pfn,
1188 : nr_scanned, nr_isolated);
1189 :
1190 : fatal_pending:
1191 0 : cc->total_migrate_scanned += nr_scanned;
1192 0 : if (nr_isolated)
1193 0 : count_compact_events(COMPACTISOLATED, nr_isolated);
1194 :
1195 0 : cc->migrate_pfn = low_pfn;
1196 :
1197 0 : return ret;
1198 : }
1199 :
1200 : /**
1201 : * isolate_migratepages_range() - isolate migrate-able pages in a PFN range
1202 : * @cc: Compaction control structure.
1203 : * @start_pfn: The first PFN to start isolating.
1204 : * @end_pfn: The one-past-last PFN.
1205 : *
1206 : * Returns -EAGAIN when contented, -EINTR in case of a signal pending, -ENOMEM
1207 : * in case we could not allocate a page, or 0.
1208 : */
1209 : int
1210 0 : isolate_migratepages_range(struct compact_control *cc, unsigned long start_pfn,
1211 : unsigned long end_pfn)
1212 : {
1213 : unsigned long pfn, block_start_pfn, block_end_pfn;
1214 0 : int ret = 0;
1215 :
1216 : /* Scan block by block. First and last block may be incomplete */
1217 0 : pfn = start_pfn;
1218 0 : block_start_pfn = pageblock_start_pfn(pfn);
1219 0 : if (block_start_pfn < cc->zone->zone_start_pfn)
1220 0 : block_start_pfn = cc->zone->zone_start_pfn;
1221 0 : block_end_pfn = pageblock_end_pfn(pfn);
1222 :
1223 0 : for (; pfn < end_pfn; pfn = block_end_pfn,
1224 0 : block_start_pfn = block_end_pfn,
1225 0 : block_end_pfn += pageblock_nr_pages) {
1226 :
1227 0 : block_end_pfn = min(block_end_pfn, end_pfn);
1228 :
1229 0 : if (!pageblock_pfn_to_page(block_start_pfn,
1230 : block_end_pfn, cc->zone))
1231 0 : continue;
1232 :
1233 0 : ret = isolate_migratepages_block(cc, pfn, block_end_pfn,
1234 : ISOLATE_UNEVICTABLE);
1235 :
1236 0 : if (ret)
1237 : break;
1238 :
1239 0 : if (cc->nr_migratepages >= COMPACT_CLUSTER_MAX)
1240 : break;
1241 : }
1242 :
1243 0 : return ret;
1244 : }
1245 :
1246 : #endif /* CONFIG_COMPACTION || CONFIG_CMA */
1247 : #ifdef CONFIG_COMPACTION
1248 :
1249 0 : static bool suitable_migration_source(struct compact_control *cc,
1250 : struct page *page)
1251 : {
1252 : int block_mt;
1253 :
1254 0 : if (pageblock_skip_persistent(page))
1255 : return false;
1256 :
1257 0 : if ((cc->mode != MIGRATE_ASYNC) || !cc->direct_compaction)
1258 : return true;
1259 :
1260 0 : block_mt = get_pageblock_migratetype(page);
1261 :
1262 0 : if (cc->migratetype == MIGRATE_MOVABLE)
1263 0 : return is_migrate_movable(block_mt);
1264 : else
1265 0 : return block_mt == cc->migratetype;
1266 : }
1267 :
1268 : /* Returns true if the page is within a block suitable for migration to */
1269 0 : static bool suitable_migration_target(struct compact_control *cc,
1270 : struct page *page)
1271 : {
1272 : /* If the page is a large free page, then disallow migration */
1273 0 : if (PageBuddy(page)) {
1274 : /*
1275 : * We are checking page_order without zone->lock taken. But
1276 : * the only small danger is that we skip a potentially suitable
1277 : * pageblock, so it's not worth to check order for valid range.
1278 : */
1279 0 : if (buddy_order_unsafe(page) >= pageblock_order)
1280 : return false;
1281 : }
1282 :
1283 0 : if (cc->ignore_block_suitable)
1284 : return true;
1285 :
1286 : /* If the block is MIGRATE_MOVABLE or MIGRATE_CMA, allow migration */
1287 0 : if (is_migrate_movable(get_pageblock_migratetype(page)))
1288 : return true;
1289 :
1290 : /* Otherwise skip the block */
1291 : return false;
1292 : }
1293 :
1294 : static inline unsigned int
1295 : freelist_scan_limit(struct compact_control *cc)
1296 : {
1297 0 : unsigned short shift = BITS_PER_LONG - 1;
1298 :
1299 0 : return (COMPACT_CLUSTER_MAX >> min(shift, cc->fast_search_fail)) + 1;
1300 : }
1301 :
1302 : /*
1303 : * Test whether the free scanner has reached the same or lower pageblock than
1304 : * the migration scanner, and compaction should thus terminate.
1305 : */
1306 : static inline bool compact_scanners_met(struct compact_control *cc)
1307 : {
1308 0 : return (cc->free_pfn >> pageblock_order)
1309 0 : <= (cc->migrate_pfn >> pageblock_order);
1310 : }
1311 :
1312 : /*
1313 : * Used when scanning for a suitable migration target which scans freelists
1314 : * in reverse. Reorders the list such as the unscanned pages are scanned
1315 : * first on the next iteration of the free scanner
1316 : */
1317 : static void
1318 0 : move_freelist_head(struct list_head *freelist, struct page *freepage)
1319 : {
1320 0 : LIST_HEAD(sublist);
1321 :
1322 0 : if (!list_is_last(freelist, &freepage->lru)) {
1323 0 : list_cut_before(&sublist, freelist, &freepage->lru);
1324 : list_splice_tail(&sublist, freelist);
1325 : }
1326 0 : }
1327 :
1328 : /*
1329 : * Similar to move_freelist_head except used by the migration scanner
1330 : * when scanning forward. It's possible for these list operations to
1331 : * move against each other if they search the free list exactly in
1332 : * lockstep.
1333 : */
1334 : static void
1335 0 : move_freelist_tail(struct list_head *freelist, struct page *freepage)
1336 : {
1337 0 : LIST_HEAD(sublist);
1338 :
1339 0 : if (!list_is_first(freelist, &freepage->lru)) {
1340 0 : list_cut_position(&sublist, freelist, &freepage->lru);
1341 : list_splice_tail(&sublist, freelist);
1342 : }
1343 0 : }
1344 :
1345 : static void
1346 0 : fast_isolate_around(struct compact_control *cc, unsigned long pfn)
1347 : {
1348 : unsigned long start_pfn, end_pfn;
1349 : struct page *page;
1350 :
1351 : /* Do not search around if there are enough pages already */
1352 0 : if (cc->nr_freepages >= cc->nr_migratepages)
1353 : return;
1354 :
1355 : /* Minimise scanning during async compaction */
1356 0 : if (cc->direct_compaction && cc->mode == MIGRATE_ASYNC)
1357 : return;
1358 :
1359 : /* Pageblock boundaries */
1360 0 : start_pfn = max(pageblock_start_pfn(pfn), cc->zone->zone_start_pfn);
1361 0 : end_pfn = min(pageblock_end_pfn(pfn), zone_end_pfn(cc->zone));
1362 :
1363 0 : page = pageblock_pfn_to_page(start_pfn, end_pfn, cc->zone);
1364 0 : if (!page)
1365 : return;
1366 :
1367 0 : isolate_freepages_block(cc, &start_pfn, end_pfn, &cc->freepages, 1, false);
1368 :
1369 : /* Skip this pageblock in the future as it's full or nearly full */
1370 0 : if (cc->nr_freepages < cc->nr_migratepages)
1371 0 : set_pageblock_skip(page);
1372 :
1373 : return;
1374 : }
1375 :
1376 : /* Search orders in round-robin fashion */
1377 : static int next_search_order(struct compact_control *cc, int order)
1378 : {
1379 0 : order--;
1380 0 : if (order < 0)
1381 0 : order = cc->order - 1;
1382 :
1383 : /* Search wrapped around? */
1384 0 : if (order == cc->search_order) {
1385 0 : cc->search_order--;
1386 0 : if (cc->search_order < 0)
1387 0 : cc->search_order = cc->order - 1;
1388 : return -1;
1389 : }
1390 :
1391 : return order;
1392 : }
1393 :
1394 : static unsigned long
1395 0 : fast_isolate_freepages(struct compact_control *cc)
1396 : {
1397 0 : unsigned int limit = max(1U, freelist_scan_limit(cc) >> 1);
1398 0 : unsigned int nr_scanned = 0;
1399 0 : unsigned long low_pfn, min_pfn, highest = 0;
1400 0 : unsigned long nr_isolated = 0;
1401 : unsigned long distance;
1402 0 : struct page *page = NULL;
1403 0 : bool scan_start = false;
1404 : int order;
1405 :
1406 : /* Full compaction passes in a negative order */
1407 0 : if (cc->order <= 0)
1408 0 : return cc->free_pfn;
1409 :
1410 : /*
1411 : * If starting the scan, use a deeper search and use the highest
1412 : * PFN found if a suitable one is not found.
1413 : */
1414 0 : if (cc->free_pfn >= cc->zone->compact_init_free_pfn) {
1415 0 : limit = pageblock_nr_pages >> 1;
1416 0 : scan_start = true;
1417 : }
1418 :
1419 : /*
1420 : * Preferred point is in the top quarter of the scan space but take
1421 : * a pfn from the top half if the search is problematic.
1422 : */
1423 0 : distance = (cc->free_pfn - cc->migrate_pfn);
1424 0 : low_pfn = pageblock_start_pfn(cc->free_pfn - (distance >> 2));
1425 0 : min_pfn = pageblock_start_pfn(cc->free_pfn - (distance >> 1));
1426 :
1427 0 : if (WARN_ON_ONCE(min_pfn > low_pfn))
1428 0 : low_pfn = min_pfn;
1429 :
1430 : /*
1431 : * Search starts from the last successful isolation order or the next
1432 : * order to search after a previous failure
1433 : */
1434 0 : cc->search_order = min_t(unsigned int, cc->order - 1, cc->search_order);
1435 :
1436 0 : for (order = cc->search_order;
1437 0 : !page && order >= 0;
1438 0 : order = next_search_order(cc, order)) {
1439 0 : struct free_area *area = &cc->zone->free_area[order];
1440 : struct list_head *freelist;
1441 : struct page *freepage;
1442 : unsigned long flags;
1443 0 : unsigned int order_scanned = 0;
1444 0 : unsigned long high_pfn = 0;
1445 :
1446 0 : if (!area->nr_free)
1447 0 : continue;
1448 :
1449 0 : spin_lock_irqsave(&cc->zone->lock, flags);
1450 0 : freelist = &area->free_list[MIGRATE_MOVABLE];
1451 0 : list_for_each_entry_reverse(freepage, freelist, lru) {
1452 : unsigned long pfn;
1453 :
1454 0 : order_scanned++;
1455 0 : nr_scanned++;
1456 0 : pfn = page_to_pfn(freepage);
1457 :
1458 0 : if (pfn >= highest)
1459 0 : highest = max(pageblock_start_pfn(pfn),
1460 : cc->zone->zone_start_pfn);
1461 :
1462 0 : if (pfn >= low_pfn) {
1463 0 : cc->fast_search_fail = 0;
1464 0 : cc->search_order = order;
1465 0 : page = freepage;
1466 0 : break;
1467 : }
1468 :
1469 0 : if (pfn >= min_pfn && pfn > high_pfn) {
1470 0 : high_pfn = pfn;
1471 :
1472 : /* Shorten the scan if a candidate is found */
1473 0 : limit >>= 1;
1474 : }
1475 :
1476 0 : if (order_scanned >= limit)
1477 : break;
1478 : }
1479 :
1480 : /* Use a minimum pfn if a preferred one was not found */
1481 0 : if (!page && high_pfn) {
1482 0 : page = pfn_to_page(high_pfn);
1483 :
1484 : /* Update freepage for the list reorder below */
1485 0 : freepage = page;
1486 : }
1487 :
1488 : /* Reorder to so a future search skips recent pages */
1489 0 : move_freelist_head(freelist, freepage);
1490 :
1491 : /* Isolate the page if available */
1492 0 : if (page) {
1493 0 : if (__isolate_free_page(page, order)) {
1494 0 : set_page_private(page, order);
1495 0 : nr_isolated = 1 << order;
1496 0 : nr_scanned += nr_isolated - 1;
1497 0 : cc->nr_freepages += nr_isolated;
1498 0 : list_add_tail(&page->lru, &cc->freepages);
1499 0 : count_compact_events(COMPACTISOLATED, nr_isolated);
1500 : } else {
1501 : /* If isolation fails, abort the search */
1502 0 : order = cc->search_order + 1;
1503 0 : page = NULL;
1504 : }
1505 : }
1506 :
1507 0 : spin_unlock_irqrestore(&cc->zone->lock, flags);
1508 :
1509 : /*
1510 : * Smaller scan on next order so the total scan is related
1511 : * to freelist_scan_limit.
1512 : */
1513 0 : if (order_scanned >= limit)
1514 0 : limit = max(1U, limit >> 1);
1515 : }
1516 :
1517 0 : if (!page) {
1518 0 : cc->fast_search_fail++;
1519 0 : if (scan_start) {
1520 : /*
1521 : * Use the highest PFN found above min. If one was
1522 : * not found, be pessimistic for direct compaction
1523 : * and use the min mark.
1524 : */
1525 0 : if (highest >= min_pfn) {
1526 0 : page = pfn_to_page(highest);
1527 0 : cc->free_pfn = highest;
1528 : } else {
1529 0 : if (cc->direct_compaction && pfn_valid(min_pfn)) {
1530 0 : page = pageblock_pfn_to_page(min_pfn,
1531 0 : min(pageblock_end_pfn(min_pfn),
1532 : zone_end_pfn(cc->zone)),
1533 : cc->zone);
1534 0 : cc->free_pfn = min_pfn;
1535 : }
1536 : }
1537 : }
1538 : }
1539 :
1540 0 : if (highest && highest >= cc->zone->compact_cached_free_pfn) {
1541 0 : highest -= pageblock_nr_pages;
1542 0 : cc->zone->compact_cached_free_pfn = highest;
1543 : }
1544 :
1545 0 : cc->total_free_scanned += nr_scanned;
1546 0 : if (!page)
1547 0 : return cc->free_pfn;
1548 :
1549 0 : low_pfn = page_to_pfn(page);
1550 0 : fast_isolate_around(cc, low_pfn);
1551 0 : return low_pfn;
1552 : }
1553 :
1554 : /*
1555 : * Based on information in the current compact_control, find blocks
1556 : * suitable for isolating free pages from and then isolate them.
1557 : */
1558 0 : static void isolate_freepages(struct compact_control *cc)
1559 : {
1560 0 : struct zone *zone = cc->zone;
1561 : struct page *page;
1562 : unsigned long block_start_pfn; /* start of current pageblock */
1563 : unsigned long isolate_start_pfn; /* exact pfn we start at */
1564 : unsigned long block_end_pfn; /* end of current pageblock */
1565 : unsigned long low_pfn; /* lowest pfn scanner is able to scan */
1566 0 : struct list_head *freelist = &cc->freepages;
1567 : unsigned int stride;
1568 :
1569 : /* Try a small search of the free lists for a candidate */
1570 0 : fast_isolate_freepages(cc);
1571 0 : if (cc->nr_freepages)
1572 : goto splitmap;
1573 :
1574 : /*
1575 : * Initialise the free scanner. The starting point is where we last
1576 : * successfully isolated from, zone-cached value, or the end of the
1577 : * zone when isolating for the first time. For looping we also need
1578 : * this pfn aligned down to the pageblock boundary, because we do
1579 : * block_start_pfn -= pageblock_nr_pages in the for loop.
1580 : * For ending point, take care when isolating in last pageblock of a
1581 : * zone which ends in the middle of a pageblock.
1582 : * The low boundary is the end of the pageblock the migration scanner
1583 : * is using.
1584 : */
1585 0 : isolate_start_pfn = cc->free_pfn;
1586 0 : block_start_pfn = pageblock_start_pfn(isolate_start_pfn);
1587 0 : block_end_pfn = min(block_start_pfn + pageblock_nr_pages,
1588 : zone_end_pfn(zone));
1589 0 : low_pfn = pageblock_end_pfn(cc->migrate_pfn);
1590 0 : stride = cc->mode == MIGRATE_ASYNC ? COMPACT_CLUSTER_MAX : 1;
1591 :
1592 : /*
1593 : * Isolate free pages until enough are available to migrate the
1594 : * pages on cc->migratepages. We stop searching if the migrate
1595 : * and free page scanners meet or enough free pages are isolated.
1596 : */
1597 0 : for (; block_start_pfn >= low_pfn;
1598 0 : block_end_pfn = block_start_pfn,
1599 0 : block_start_pfn -= pageblock_nr_pages,
1600 0 : isolate_start_pfn = block_start_pfn) {
1601 : unsigned long nr_isolated;
1602 :
1603 : /*
1604 : * This can iterate a massively long zone without finding any
1605 : * suitable migration targets, so periodically check resched.
1606 : */
1607 0 : if (!(block_start_pfn % (COMPACT_CLUSTER_MAX * pageblock_nr_pages)))
1608 0 : cond_resched();
1609 :
1610 0 : page = pageblock_pfn_to_page(block_start_pfn, block_end_pfn,
1611 : zone);
1612 0 : if (!page)
1613 0 : continue;
1614 :
1615 : /* Check the block is suitable for migration */
1616 0 : if (!suitable_migration_target(cc, page))
1617 0 : continue;
1618 :
1619 : /* If isolation recently failed, do not retry */
1620 0 : if (!isolation_suitable(cc, page))
1621 0 : continue;
1622 :
1623 : /* Found a block suitable for isolating free pages from. */
1624 0 : nr_isolated = isolate_freepages_block(cc, &isolate_start_pfn,
1625 : block_end_pfn, freelist, stride, false);
1626 :
1627 : /* Update the skip hint if the full pageblock was scanned */
1628 0 : if (isolate_start_pfn == block_end_pfn)
1629 0 : update_pageblock_skip(cc, page, block_start_pfn);
1630 :
1631 : /* Are enough freepages isolated? */
1632 0 : if (cc->nr_freepages >= cc->nr_migratepages) {
1633 0 : if (isolate_start_pfn >= block_end_pfn) {
1634 : /*
1635 : * Restart at previous pageblock if more
1636 : * freepages can be isolated next time.
1637 : */
1638 0 : isolate_start_pfn =
1639 0 : block_start_pfn - pageblock_nr_pages;
1640 : }
1641 : break;
1642 0 : } else if (isolate_start_pfn < block_end_pfn) {
1643 : /*
1644 : * If isolation failed early, do not continue
1645 : * needlessly.
1646 : */
1647 : break;
1648 : }
1649 :
1650 : /* Adjust stride depending on isolation */
1651 0 : if (nr_isolated) {
1652 0 : stride = 1;
1653 0 : continue;
1654 : }
1655 0 : stride = min_t(unsigned int, COMPACT_CLUSTER_MAX, stride << 1);
1656 : }
1657 :
1658 : /*
1659 : * Record where the free scanner will restart next time. Either we
1660 : * broke from the loop and set isolate_start_pfn based on the last
1661 : * call to isolate_freepages_block(), or we met the migration scanner
1662 : * and the loop terminated due to isolate_start_pfn < low_pfn
1663 : */
1664 0 : cc->free_pfn = isolate_start_pfn;
1665 :
1666 : splitmap:
1667 : /* __isolate_free_page() does not map the pages */
1668 0 : split_map_pages(freelist);
1669 0 : }
1670 :
1671 : /*
1672 : * This is a migrate-callback that "allocates" freepages by taking pages
1673 : * from the isolated freelists in the block we are migrating to.
1674 : */
1675 0 : static struct page *compaction_alloc(struct page *migratepage,
1676 : unsigned long data)
1677 : {
1678 0 : struct compact_control *cc = (struct compact_control *)data;
1679 : struct page *freepage;
1680 :
1681 0 : if (list_empty(&cc->freepages)) {
1682 0 : isolate_freepages(cc);
1683 :
1684 0 : if (list_empty(&cc->freepages))
1685 : return NULL;
1686 : }
1687 :
1688 0 : freepage = list_entry(cc->freepages.next, struct page, lru);
1689 0 : list_del(&freepage->lru);
1690 0 : cc->nr_freepages--;
1691 :
1692 0 : return freepage;
1693 : }
1694 :
1695 : /*
1696 : * This is a migrate-callback that "frees" freepages back to the isolated
1697 : * freelist. All pages on the freelist are from the same zone, so there is no
1698 : * special handling needed for NUMA.
1699 : */
1700 0 : static void compaction_free(struct page *page, unsigned long data)
1701 : {
1702 0 : struct compact_control *cc = (struct compact_control *)data;
1703 :
1704 0 : list_add(&page->lru, &cc->freepages);
1705 0 : cc->nr_freepages++;
1706 0 : }
1707 :
1708 : /* possible outcome of isolate_migratepages */
1709 : typedef enum {
1710 : ISOLATE_ABORT, /* Abort compaction now */
1711 : ISOLATE_NONE, /* No pages isolated, continue scanning */
1712 : ISOLATE_SUCCESS, /* Pages isolated, migrate */
1713 : } isolate_migrate_t;
1714 :
1715 : /*
1716 : * Allow userspace to control policy on scanning the unevictable LRU for
1717 : * compactable pages.
1718 : */
1719 : int sysctl_compact_unevictable_allowed __read_mostly = CONFIG_COMPACT_UNEVICTABLE_DEFAULT;
1720 :
1721 : static inline void
1722 : update_fast_start_pfn(struct compact_control *cc, unsigned long pfn)
1723 : {
1724 0 : if (cc->fast_start_pfn == ULONG_MAX)
1725 : return;
1726 :
1727 0 : if (!cc->fast_start_pfn)
1728 0 : cc->fast_start_pfn = pfn;
1729 :
1730 0 : cc->fast_start_pfn = min(cc->fast_start_pfn, pfn);
1731 : }
1732 :
1733 : static inline unsigned long
1734 : reinit_migrate_pfn(struct compact_control *cc)
1735 : {
1736 0 : if (!cc->fast_start_pfn || cc->fast_start_pfn == ULONG_MAX)
1737 0 : return cc->migrate_pfn;
1738 :
1739 0 : cc->migrate_pfn = cc->fast_start_pfn;
1740 0 : cc->fast_start_pfn = ULONG_MAX;
1741 :
1742 : return cc->migrate_pfn;
1743 : }
1744 :
1745 : /*
1746 : * Briefly search the free lists for a migration source that already has
1747 : * some free pages to reduce the number of pages that need migration
1748 : * before a pageblock is free.
1749 : */
1750 0 : static unsigned long fast_find_migrateblock(struct compact_control *cc)
1751 : {
1752 0 : unsigned int limit = freelist_scan_limit(cc);
1753 0 : unsigned int nr_scanned = 0;
1754 : unsigned long distance;
1755 0 : unsigned long pfn = cc->migrate_pfn;
1756 : unsigned long high_pfn;
1757 : int order;
1758 0 : bool found_block = false;
1759 :
1760 : /* Skip hints are relied on to avoid repeats on the fast search */
1761 0 : if (cc->ignore_skip_hint)
1762 : return pfn;
1763 :
1764 : /*
1765 : * If the pageblock should be finished then do not select a different
1766 : * pageblock.
1767 : */
1768 0 : if (cc->finish_pageblock)
1769 : return pfn;
1770 :
1771 : /*
1772 : * If the migrate_pfn is not at the start of a zone or the start
1773 : * of a pageblock then assume this is a continuation of a previous
1774 : * scan restarted due to COMPACT_CLUSTER_MAX.
1775 : */
1776 0 : if (pfn != cc->zone->zone_start_pfn && pfn != pageblock_start_pfn(pfn))
1777 : return pfn;
1778 :
1779 : /*
1780 : * For smaller orders, just linearly scan as the number of pages
1781 : * to migrate should be relatively small and does not necessarily
1782 : * justify freeing up a large block for a small allocation.
1783 : */
1784 0 : if (cc->order <= PAGE_ALLOC_COSTLY_ORDER)
1785 : return pfn;
1786 :
1787 : /*
1788 : * Only allow kcompactd and direct requests for movable pages to
1789 : * quickly clear out a MOVABLE pageblock for allocation. This
1790 : * reduces the risk that a large movable pageblock is freed for
1791 : * an unmovable/reclaimable small allocation.
1792 : */
1793 0 : if (cc->direct_compaction && cc->migratetype != MIGRATE_MOVABLE)
1794 : return pfn;
1795 :
1796 : /*
1797 : * When starting the migration scanner, pick any pageblock within the
1798 : * first half of the search space. Otherwise try and pick a pageblock
1799 : * within the first eighth to reduce the chances that a migration
1800 : * target later becomes a source.
1801 : */
1802 0 : distance = (cc->free_pfn - cc->migrate_pfn) >> 1;
1803 0 : if (cc->migrate_pfn != cc->zone->zone_start_pfn)
1804 0 : distance >>= 2;
1805 0 : high_pfn = pageblock_start_pfn(cc->migrate_pfn + distance);
1806 :
1807 0 : for (order = cc->order - 1;
1808 0 : order >= PAGE_ALLOC_COSTLY_ORDER && !found_block && nr_scanned < limit;
1809 0 : order--) {
1810 0 : struct free_area *area = &cc->zone->free_area[order];
1811 : struct list_head *freelist;
1812 : unsigned long flags;
1813 : struct page *freepage;
1814 :
1815 0 : if (!area->nr_free)
1816 0 : continue;
1817 :
1818 0 : spin_lock_irqsave(&cc->zone->lock, flags);
1819 0 : freelist = &area->free_list[MIGRATE_MOVABLE];
1820 0 : list_for_each_entry(freepage, freelist, lru) {
1821 : unsigned long free_pfn;
1822 :
1823 0 : if (nr_scanned++ >= limit) {
1824 0 : move_freelist_tail(freelist, freepage);
1825 0 : break;
1826 : }
1827 :
1828 0 : free_pfn = page_to_pfn(freepage);
1829 0 : if (free_pfn < high_pfn) {
1830 : /*
1831 : * Avoid if skipped recently. Ideally it would
1832 : * move to the tail but even safe iteration of
1833 : * the list assumes an entry is deleted, not
1834 : * reordered.
1835 : */
1836 0 : if (get_pageblock_skip(freepage))
1837 0 : continue;
1838 :
1839 : /* Reorder to so a future search skips recent pages */
1840 0 : move_freelist_tail(freelist, freepage);
1841 :
1842 0 : update_fast_start_pfn(cc, free_pfn);
1843 0 : pfn = pageblock_start_pfn(free_pfn);
1844 0 : if (pfn < cc->zone->zone_start_pfn)
1845 0 : pfn = cc->zone->zone_start_pfn;
1846 0 : cc->fast_search_fail = 0;
1847 0 : found_block = true;
1848 0 : set_pageblock_skip(freepage);
1849 0 : break;
1850 : }
1851 : }
1852 0 : spin_unlock_irqrestore(&cc->zone->lock, flags);
1853 : }
1854 :
1855 0 : cc->total_migrate_scanned += nr_scanned;
1856 :
1857 : /*
1858 : * If fast scanning failed then use a cached entry for a page block
1859 : * that had free pages as the basis for starting a linear scan.
1860 : */
1861 0 : if (!found_block) {
1862 0 : cc->fast_search_fail++;
1863 0 : pfn = reinit_migrate_pfn(cc);
1864 : }
1865 : return pfn;
1866 : }
1867 :
1868 : /*
1869 : * Isolate all pages that can be migrated from the first suitable block,
1870 : * starting at the block pointed to by the migrate scanner pfn within
1871 : * compact_control.
1872 : */
1873 0 : static isolate_migrate_t isolate_migratepages(struct compact_control *cc)
1874 : {
1875 : unsigned long block_start_pfn;
1876 : unsigned long block_end_pfn;
1877 : unsigned long low_pfn;
1878 : struct page *page;
1879 0 : const isolate_mode_t isolate_mode =
1880 0 : (sysctl_compact_unevictable_allowed ? ISOLATE_UNEVICTABLE : 0) |
1881 0 : (cc->mode != MIGRATE_SYNC ? ISOLATE_ASYNC_MIGRATE : 0);
1882 : bool fast_find_block;
1883 :
1884 : /*
1885 : * Start at where we last stopped, or beginning of the zone as
1886 : * initialized by compact_zone(). The first failure will use
1887 : * the lowest PFN as the starting point for linear scanning.
1888 : */
1889 0 : low_pfn = fast_find_migrateblock(cc);
1890 0 : block_start_pfn = pageblock_start_pfn(low_pfn);
1891 0 : if (block_start_pfn < cc->zone->zone_start_pfn)
1892 0 : block_start_pfn = cc->zone->zone_start_pfn;
1893 :
1894 : /*
1895 : * fast_find_migrateblock marks a pageblock skipped so to avoid
1896 : * the isolation_suitable check below, check whether the fast
1897 : * search was successful.
1898 : */
1899 0 : fast_find_block = low_pfn != cc->migrate_pfn && !cc->fast_search_fail;
1900 :
1901 : /* Only scan within a pageblock boundary */
1902 0 : block_end_pfn = pageblock_end_pfn(low_pfn);
1903 :
1904 : /*
1905 : * Iterate over whole pageblocks until we find the first suitable.
1906 : * Do not cross the free scanner.
1907 : */
1908 0 : for (; block_end_pfn <= cc->free_pfn;
1909 0 : fast_find_block = false,
1910 0 : cc->migrate_pfn = low_pfn = block_end_pfn,
1911 0 : block_start_pfn = block_end_pfn,
1912 0 : block_end_pfn += pageblock_nr_pages) {
1913 :
1914 : /*
1915 : * This can potentially iterate a massively long zone with
1916 : * many pageblocks unsuitable, so periodically check if we
1917 : * need to schedule.
1918 : */
1919 0 : if (!(low_pfn % (COMPACT_CLUSTER_MAX * pageblock_nr_pages)))
1920 0 : cond_resched();
1921 :
1922 0 : page = pageblock_pfn_to_page(block_start_pfn,
1923 : block_end_pfn, cc->zone);
1924 0 : if (!page)
1925 0 : continue;
1926 :
1927 : /*
1928 : * If isolation recently failed, do not retry. Only check the
1929 : * pageblock once. COMPACT_CLUSTER_MAX causes a pageblock
1930 : * to be visited multiple times. Assume skip was checked
1931 : * before making it "skip" so other compaction instances do
1932 : * not scan the same block.
1933 : */
1934 0 : if (pageblock_aligned(low_pfn) &&
1935 0 : !fast_find_block && !isolation_suitable(cc, page))
1936 0 : continue;
1937 :
1938 : /*
1939 : * For async direct compaction, only scan the pageblocks of the
1940 : * same migratetype without huge pages. Async direct compaction
1941 : * is optimistic to see if the minimum amount of work satisfies
1942 : * the allocation. The cached PFN is updated as it's possible
1943 : * that all remaining blocks between source and target are
1944 : * unsuitable and the compaction scanners fail to meet.
1945 : */
1946 0 : if (!suitable_migration_source(cc, page)) {
1947 0 : update_cached_migrate(cc, block_end_pfn);
1948 0 : continue;
1949 : }
1950 :
1951 : /* Perform the isolation */
1952 0 : if (isolate_migratepages_block(cc, low_pfn, block_end_pfn,
1953 : isolate_mode))
1954 : return ISOLATE_ABORT;
1955 :
1956 : /*
1957 : * Either we isolated something and proceed with migration. Or
1958 : * we failed and compact_zone should decide if we should
1959 : * continue or not.
1960 : */
1961 : break;
1962 : }
1963 :
1964 0 : return cc->nr_migratepages ? ISOLATE_SUCCESS : ISOLATE_NONE;
1965 : }
1966 :
1967 : /*
1968 : * order == -1 is expected when compacting via
1969 : * /proc/sys/vm/compact_memory
1970 : */
1971 : static inline bool is_via_compact_memory(int order)
1972 : {
1973 : return order == -1;
1974 : }
1975 :
1976 : /*
1977 : * Determine whether kswapd is (or recently was!) running on this node.
1978 : *
1979 : * pgdat_kswapd_lock() pins pgdat->kswapd, so a concurrent kswapd_stop() can't
1980 : * zero it.
1981 : */
1982 : static bool kswapd_is_running(pg_data_t *pgdat)
1983 : {
1984 : bool running;
1985 :
1986 51 : pgdat_kswapd_lock(pgdat);
1987 51 : running = pgdat->kswapd && task_is_running(pgdat->kswapd);
1988 51 : pgdat_kswapd_unlock(pgdat);
1989 :
1990 : return running;
1991 : }
1992 :
1993 : /*
1994 : * A zone's fragmentation score is the external fragmentation wrt to the
1995 : * COMPACTION_HPAGE_ORDER. It returns a value in the range [0, 100].
1996 : */
1997 : static unsigned int fragmentation_score_zone(struct zone *zone)
1998 : {
1999 51 : return extfrag_for_order(zone, COMPACTION_HPAGE_ORDER);
2000 : }
2001 :
2002 : /*
2003 : * A weighted zone's fragmentation score is the external fragmentation
2004 : * wrt to the COMPACTION_HPAGE_ORDER scaled by the zone's size. It
2005 : * returns a value in the range [0, 100].
2006 : *
2007 : * The scaling factor ensures that proactive compaction focuses on larger
2008 : * zones like ZONE_NORMAL, rather than smaller, specialized zones like
2009 : * ZONE_DMA32. For smaller zones, the score value remains close to zero,
2010 : * and thus never exceeds the high threshold for proactive compaction.
2011 : */
2012 : static unsigned int fragmentation_score_zone_weighted(struct zone *zone)
2013 : {
2014 : unsigned long score;
2015 :
2016 102 : score = zone->present_pages * fragmentation_score_zone(zone);
2017 102 : return div64_ul(score, zone->zone_pgdat->node_present_pages + 1);
2018 : }
2019 :
2020 : /*
2021 : * The per-node proactive (background) compaction process is started by its
2022 : * corresponding kcompactd thread when the node's fragmentation score
2023 : * exceeds the high threshold. The compaction process remains active till
2024 : * the node's score falls below the low threshold, or one of the back-off
2025 : * conditions is met.
2026 : */
2027 51 : static unsigned int fragmentation_score_node(pg_data_t *pgdat)
2028 : {
2029 51 : unsigned int score = 0;
2030 : int zoneid;
2031 :
2032 153 : for (zoneid = 0; zoneid < MAX_NR_ZONES; zoneid++) {
2033 : struct zone *zone;
2034 :
2035 102 : zone = &pgdat->node_zones[zoneid];
2036 102 : if (!populated_zone(zone))
2037 51 : continue;
2038 51 : score += fragmentation_score_zone_weighted(zone);
2039 : }
2040 :
2041 51 : return score;
2042 : }
2043 :
2044 : static unsigned int fragmentation_score_wmark(pg_data_t *pgdat, bool low)
2045 : {
2046 : unsigned int wmark_low;
2047 :
2048 : /*
2049 : * Cap the low watermark to avoid excessive compaction
2050 : * activity in case a user sets the proactiveness tunable
2051 : * close to 100 (maximum).
2052 : */
2053 51 : wmark_low = max(100U - sysctl_compaction_proactiveness, 5U);
2054 51 : return low ? wmark_low : min(wmark_low + 10, 100U);
2055 : }
2056 :
2057 51 : static bool should_proactive_compact_node(pg_data_t *pgdat)
2058 : {
2059 : int wmark_high;
2060 :
2061 102 : if (!sysctl_compaction_proactiveness || kswapd_is_running(pgdat))
2062 : return false;
2063 :
2064 51 : wmark_high = fragmentation_score_wmark(pgdat, false);
2065 51 : return fragmentation_score_node(pgdat) > wmark_high;
2066 : }
2067 :
2068 0 : static enum compact_result __compact_finished(struct compact_control *cc)
2069 : {
2070 : unsigned int order;
2071 0 : const int migratetype = cc->migratetype;
2072 : int ret;
2073 :
2074 : /* Compaction run completes if the migrate and free scanner meet */
2075 0 : if (compact_scanners_met(cc)) {
2076 : /* Let the next compaction start anew. */
2077 0 : reset_cached_positions(cc->zone);
2078 :
2079 : /*
2080 : * Mark that the PG_migrate_skip information should be cleared
2081 : * by kswapd when it goes to sleep. kcompactd does not set the
2082 : * flag itself as the decision to be clear should be directly
2083 : * based on an allocation request.
2084 : */
2085 0 : if (cc->direct_compaction)
2086 0 : cc->zone->compact_blockskip_flush = true;
2087 :
2088 0 : if (cc->whole_zone)
2089 : return COMPACT_COMPLETE;
2090 : else
2091 0 : return COMPACT_PARTIAL_SKIPPED;
2092 : }
2093 :
2094 0 : if (cc->proactive_compaction) {
2095 : int score, wmark_low;
2096 : pg_data_t *pgdat;
2097 :
2098 0 : pgdat = cc->zone->zone_pgdat;
2099 0 : if (kswapd_is_running(pgdat))
2100 : return COMPACT_PARTIAL_SKIPPED;
2101 :
2102 0 : score = fragmentation_score_zone(cc->zone);
2103 0 : wmark_low = fragmentation_score_wmark(pgdat, true);
2104 :
2105 0 : if (score > wmark_low)
2106 : ret = COMPACT_CONTINUE;
2107 : else
2108 0 : ret = COMPACT_SUCCESS;
2109 :
2110 : goto out;
2111 : }
2112 :
2113 0 : if (is_via_compact_memory(cc->order))
2114 : return COMPACT_CONTINUE;
2115 :
2116 : /*
2117 : * Always finish scanning a pageblock to reduce the possibility of
2118 : * fallbacks in the future. This is particularly important when
2119 : * migration source is unmovable/reclaimable but it's not worth
2120 : * special casing.
2121 : */
2122 0 : if (!pageblock_aligned(cc->migrate_pfn))
2123 : return COMPACT_CONTINUE;
2124 :
2125 : /* Direct compactor: Is a suitable page free? */
2126 0 : ret = COMPACT_NO_SUITABLE_PAGE;
2127 0 : for (order = cc->order; order < MAX_ORDER; order++) {
2128 0 : struct free_area *area = &cc->zone->free_area[order];
2129 : bool can_steal;
2130 :
2131 : /* Job done if page is free of the right migratetype */
2132 0 : if (!free_area_empty(area, migratetype))
2133 0 : return COMPACT_SUCCESS;
2134 :
2135 : #ifdef CONFIG_CMA
2136 : /* MIGRATE_MOVABLE can fallback on MIGRATE_CMA */
2137 : if (migratetype == MIGRATE_MOVABLE &&
2138 : !free_area_empty(area, MIGRATE_CMA))
2139 : return COMPACT_SUCCESS;
2140 : #endif
2141 : /*
2142 : * Job done if allocation would steal freepages from
2143 : * other migratetype buddy lists.
2144 : */
2145 0 : if (find_suitable_fallback(area, order, migratetype,
2146 : true, &can_steal) != -1)
2147 : /*
2148 : * Movable pages are OK in any pageblock. If we are
2149 : * stealing for a non-movable allocation, make sure
2150 : * we finish compacting the current pageblock first
2151 : * (which is assured by the above migrate_pfn align
2152 : * check) so it is as free as possible and we won't
2153 : * have to steal another one soon.
2154 : */
2155 : return COMPACT_SUCCESS;
2156 : }
2157 :
2158 : out:
2159 0 : if (cc->contended || fatal_signal_pending(current))
2160 : ret = COMPACT_CONTENDED;
2161 :
2162 0 : return ret;
2163 : }
2164 :
2165 : static enum compact_result compact_finished(struct compact_control *cc)
2166 : {
2167 : int ret;
2168 :
2169 0 : ret = __compact_finished(cc);
2170 0 : trace_mm_compaction_finished(cc->zone, cc->order, ret);
2171 0 : if (ret == COMPACT_NO_SUITABLE_PAGE)
2172 0 : ret = COMPACT_CONTINUE;
2173 :
2174 0 : return ret;
2175 : }
2176 :
2177 0 : static enum compact_result __compaction_suitable(struct zone *zone, int order,
2178 : unsigned int alloc_flags,
2179 : int highest_zoneidx,
2180 : unsigned long wmark_target)
2181 : {
2182 : unsigned long watermark;
2183 :
2184 0 : if (is_via_compact_memory(order))
2185 : return COMPACT_CONTINUE;
2186 :
2187 0 : watermark = wmark_pages(zone, alloc_flags & ALLOC_WMARK_MASK);
2188 : /*
2189 : * If watermarks for high-order allocation are already met, there
2190 : * should be no need for compaction at all.
2191 : */
2192 0 : if (zone_watermark_ok(zone, order, watermark, highest_zoneidx,
2193 : alloc_flags))
2194 : return COMPACT_SUCCESS;
2195 :
2196 : /*
2197 : * Watermarks for order-0 must be met for compaction to be able to
2198 : * isolate free pages for migration targets. This means that the
2199 : * watermark and alloc_flags have to match, or be more pessimistic than
2200 : * the check in __isolate_free_page(). We don't use the direct
2201 : * compactor's alloc_flags, as they are not relevant for freepage
2202 : * isolation. We however do use the direct compactor's highest_zoneidx
2203 : * to skip over zones where lowmem reserves would prevent allocation
2204 : * even if compaction succeeds.
2205 : * For costly orders, we require low watermark instead of min for
2206 : * compaction to proceed to increase its chances.
2207 : * ALLOC_CMA is used, as pages in CMA pageblocks are considered
2208 : * suitable migration targets
2209 : */
2210 0 : watermark = (order > PAGE_ALLOC_COSTLY_ORDER) ?
2211 0 : low_wmark_pages(zone) : min_wmark_pages(zone);
2212 0 : watermark += compact_gap(order);
2213 0 : if (!__zone_watermark_ok(zone, 0, watermark, highest_zoneidx,
2214 : ALLOC_CMA, wmark_target))
2215 : return COMPACT_SKIPPED;
2216 :
2217 0 : return COMPACT_CONTINUE;
2218 : }
2219 :
2220 : /*
2221 : * compaction_suitable: Is this suitable to run compaction on this zone now?
2222 : * Returns
2223 : * COMPACT_SKIPPED - If there are too few free pages for compaction
2224 : * COMPACT_SUCCESS - If the allocation would succeed without compaction
2225 : * COMPACT_CONTINUE - If compaction should run now
2226 : */
2227 0 : enum compact_result compaction_suitable(struct zone *zone, int order,
2228 : unsigned int alloc_flags,
2229 : int highest_zoneidx)
2230 : {
2231 : enum compact_result ret;
2232 : int fragindex;
2233 :
2234 0 : ret = __compaction_suitable(zone, order, alloc_flags, highest_zoneidx,
2235 : zone_page_state(zone, NR_FREE_PAGES));
2236 : /*
2237 : * fragmentation index determines if allocation failures are due to
2238 : * low memory or external fragmentation
2239 : *
2240 : * index of -1000 would imply allocations might succeed depending on
2241 : * watermarks, but we already failed the high-order watermark check
2242 : * index towards 0 implies failure is due to lack of memory
2243 : * index towards 1000 implies failure is due to fragmentation
2244 : *
2245 : * Only compact if a failure would be due to fragmentation. Also
2246 : * ignore fragindex for non-costly orders where the alternative to
2247 : * a successful reclaim/compaction is OOM. Fragindex and the
2248 : * vm.extfrag_threshold sysctl is meant as a heuristic to prevent
2249 : * excessive compaction for costly orders, but it should not be at the
2250 : * expense of system stability.
2251 : */
2252 0 : if (ret == COMPACT_CONTINUE && (order > PAGE_ALLOC_COSTLY_ORDER)) {
2253 0 : fragindex = fragmentation_index(zone, order);
2254 0 : if (fragindex >= 0 && fragindex <= sysctl_extfrag_threshold)
2255 0 : ret = COMPACT_NOT_SUITABLE_ZONE;
2256 : }
2257 :
2258 0 : trace_mm_compaction_suitable(zone, order, ret);
2259 0 : if (ret == COMPACT_NOT_SUITABLE_ZONE)
2260 0 : ret = COMPACT_SKIPPED;
2261 :
2262 0 : return ret;
2263 : }
2264 :
2265 0 : bool compaction_zonelist_suitable(struct alloc_context *ac, int order,
2266 : int alloc_flags)
2267 : {
2268 : struct zone *zone;
2269 : struct zoneref *z;
2270 :
2271 : /*
2272 : * Make sure at least one zone would pass __compaction_suitable if we continue
2273 : * retrying the reclaim.
2274 : */
2275 0 : for_each_zone_zonelist_nodemask(zone, z, ac->zonelist,
2276 : ac->highest_zoneidx, ac->nodemask) {
2277 : unsigned long available;
2278 : enum compact_result compact_result;
2279 :
2280 : /*
2281 : * Do not consider all the reclaimable memory because we do not
2282 : * want to trash just for a single high order allocation which
2283 : * is even not guaranteed to appear even if __compaction_suitable
2284 : * is happy about the watermark check.
2285 : */
2286 0 : available = zone_reclaimable_pages(zone) / order;
2287 0 : available += zone_page_state_snapshot(zone, NR_FREE_PAGES);
2288 0 : compact_result = __compaction_suitable(zone, order, alloc_flags,
2289 0 : ac->highest_zoneidx, available);
2290 0 : if (compact_result == COMPACT_CONTINUE)
2291 : return true;
2292 : }
2293 :
2294 : return false;
2295 : }
2296 :
2297 : static enum compact_result
2298 0 : compact_zone(struct compact_control *cc, struct capture_control *capc)
2299 : {
2300 : enum compact_result ret;
2301 0 : unsigned long start_pfn = cc->zone->zone_start_pfn;
2302 0 : unsigned long end_pfn = zone_end_pfn(cc->zone);
2303 : unsigned long last_migrated_pfn;
2304 0 : const bool sync = cc->mode != MIGRATE_ASYNC;
2305 : bool update_cached;
2306 0 : unsigned int nr_succeeded = 0;
2307 :
2308 : /*
2309 : * These counters track activities during zone compaction. Initialize
2310 : * them before compacting a new zone.
2311 : */
2312 0 : cc->total_migrate_scanned = 0;
2313 0 : cc->total_free_scanned = 0;
2314 0 : cc->nr_migratepages = 0;
2315 0 : cc->nr_freepages = 0;
2316 0 : INIT_LIST_HEAD(&cc->freepages);
2317 0 : INIT_LIST_HEAD(&cc->migratepages);
2318 :
2319 0 : cc->migratetype = gfp_migratetype(cc->gfp_mask);
2320 0 : ret = compaction_suitable(cc->zone, cc->order, cc->alloc_flags,
2321 : cc->highest_zoneidx);
2322 : /* Compaction is likely to fail */
2323 0 : if (ret == COMPACT_SUCCESS || ret == COMPACT_SKIPPED)
2324 : return ret;
2325 :
2326 : /*
2327 : * Clear pageblock skip if there were failures recently and compaction
2328 : * is about to be retried after being deferred.
2329 : */
2330 0 : if (compaction_restarting(cc->zone, cc->order))
2331 0 : __reset_isolation_suitable(cc->zone);
2332 :
2333 : /*
2334 : * Setup to move all movable pages to the end of the zone. Used cached
2335 : * information on where the scanners should start (unless we explicitly
2336 : * want to compact the whole zone), but check that it is initialised
2337 : * by ensuring the values are within zone boundaries.
2338 : */
2339 0 : cc->fast_start_pfn = 0;
2340 0 : if (cc->whole_zone) {
2341 0 : cc->migrate_pfn = start_pfn;
2342 0 : cc->free_pfn = pageblock_start_pfn(end_pfn - 1);
2343 : } else {
2344 0 : cc->migrate_pfn = cc->zone->compact_cached_migrate_pfn[sync];
2345 0 : cc->free_pfn = cc->zone->compact_cached_free_pfn;
2346 0 : if (cc->free_pfn < start_pfn || cc->free_pfn >= end_pfn) {
2347 0 : cc->free_pfn = pageblock_start_pfn(end_pfn - 1);
2348 0 : cc->zone->compact_cached_free_pfn = cc->free_pfn;
2349 : }
2350 0 : if (cc->migrate_pfn < start_pfn || cc->migrate_pfn >= end_pfn) {
2351 0 : cc->migrate_pfn = start_pfn;
2352 0 : cc->zone->compact_cached_migrate_pfn[0] = cc->migrate_pfn;
2353 0 : cc->zone->compact_cached_migrate_pfn[1] = cc->migrate_pfn;
2354 : }
2355 :
2356 0 : if (cc->migrate_pfn <= cc->zone->compact_init_migrate_pfn)
2357 0 : cc->whole_zone = true;
2358 : }
2359 :
2360 0 : last_migrated_pfn = 0;
2361 :
2362 : /*
2363 : * Migrate has separate cached PFNs for ASYNC and SYNC* migration on
2364 : * the basis that some migrations will fail in ASYNC mode. However,
2365 : * if the cached PFNs match and pageblocks are skipped due to having
2366 : * no isolation candidates, then the sync state does not matter.
2367 : * Until a pageblock with isolation candidates is found, keep the
2368 : * cached PFNs in sync to avoid revisiting the same blocks.
2369 : */
2370 0 : update_cached = !sync &&
2371 0 : cc->zone->compact_cached_migrate_pfn[0] == cc->zone->compact_cached_migrate_pfn[1];
2372 :
2373 0 : trace_mm_compaction_begin(cc, start_pfn, end_pfn, sync);
2374 :
2375 : /* lru_add_drain_all could be expensive with involving other CPUs */
2376 0 : lru_add_drain();
2377 :
2378 0 : while ((ret = compact_finished(cc)) == COMPACT_CONTINUE) {
2379 : int err;
2380 0 : unsigned long iteration_start_pfn = cc->migrate_pfn;
2381 :
2382 : /*
2383 : * Avoid multiple rescans of the same pageblock which can
2384 : * happen if a page cannot be isolated (dirty/writeback in
2385 : * async mode) or if the migrated pages are being allocated
2386 : * before the pageblock is cleared. The first rescan will
2387 : * capture the entire pageblock for migration. If it fails,
2388 : * it'll be marked skip and scanning will proceed as normal.
2389 : */
2390 0 : cc->finish_pageblock = false;
2391 0 : if (pageblock_start_pfn(last_migrated_pfn) ==
2392 : pageblock_start_pfn(iteration_start_pfn)) {
2393 0 : cc->finish_pageblock = true;
2394 : }
2395 :
2396 : rescan:
2397 0 : switch (isolate_migratepages(cc)) {
2398 : case ISOLATE_ABORT:
2399 0 : ret = COMPACT_CONTENDED;
2400 0 : putback_movable_pages(&cc->migratepages);
2401 0 : cc->nr_migratepages = 0;
2402 0 : goto out;
2403 : case ISOLATE_NONE:
2404 0 : if (update_cached) {
2405 0 : cc->zone->compact_cached_migrate_pfn[1] =
2406 0 : cc->zone->compact_cached_migrate_pfn[0];
2407 : }
2408 :
2409 : /*
2410 : * We haven't isolated and migrated anything, but
2411 : * there might still be unflushed migrations from
2412 : * previous cc->order aligned block.
2413 : */
2414 : goto check_drain;
2415 : case ISOLATE_SUCCESS:
2416 0 : update_cached = false;
2417 0 : last_migrated_pfn = iteration_start_pfn;
2418 : }
2419 :
2420 0 : err = migrate_pages(&cc->migratepages, compaction_alloc,
2421 : compaction_free, (unsigned long)cc, cc->mode,
2422 : MR_COMPACTION, &nr_succeeded);
2423 :
2424 0 : trace_mm_compaction_migratepages(cc, nr_succeeded);
2425 :
2426 : /* All pages were either migrated or will be released */
2427 0 : cc->nr_migratepages = 0;
2428 0 : if (err) {
2429 0 : putback_movable_pages(&cc->migratepages);
2430 : /*
2431 : * migrate_pages() may return -ENOMEM when scanners meet
2432 : * and we want compact_finished() to detect it
2433 : */
2434 0 : if (err == -ENOMEM && !compact_scanners_met(cc)) {
2435 : ret = COMPACT_CONTENDED;
2436 : goto out;
2437 : }
2438 : /*
2439 : * If an ASYNC or SYNC_LIGHT fails to migrate a page
2440 : * within the current order-aligned block, scan the
2441 : * remainder of the pageblock. This will mark the
2442 : * pageblock "skip" to avoid rescanning in the near
2443 : * future. This will isolate more pages than necessary
2444 : * for the request but avoid loops due to
2445 : * fast_find_migrateblock revisiting blocks that were
2446 : * recently partially scanned.
2447 : */
2448 0 : if (cc->direct_compaction && !cc->finish_pageblock &&
2449 0 : (cc->mode < MIGRATE_SYNC)) {
2450 0 : cc->finish_pageblock = true;
2451 :
2452 : /*
2453 : * Draining pcplists does not help THP if
2454 : * any page failed to migrate. Even after
2455 : * drain, the pageblock will not be free.
2456 : */
2457 0 : if (cc->order == COMPACTION_HPAGE_ORDER)
2458 0 : last_migrated_pfn = 0;
2459 :
2460 : goto rescan;
2461 : }
2462 : }
2463 :
2464 : /* Stop if a page has been captured */
2465 0 : if (capc && capc->page) {
2466 : ret = COMPACT_SUCCESS;
2467 : break;
2468 : }
2469 :
2470 : check_drain:
2471 : /*
2472 : * Has the migration scanner moved away from the previous
2473 : * cc->order aligned block where we migrated from? If yes,
2474 : * flush the pages that were freed, so that they can merge and
2475 : * compact_finished() can detect immediately if allocation
2476 : * would succeed.
2477 : */
2478 0 : if (cc->order > 0 && last_migrated_pfn) {
2479 0 : unsigned long current_block_start =
2480 0 : block_start_pfn(cc->migrate_pfn, cc->order);
2481 :
2482 0 : if (last_migrated_pfn < current_block_start) {
2483 0 : lru_add_drain_cpu_zone(cc->zone);
2484 : /* No more flushing until we migrate again */
2485 0 : last_migrated_pfn = 0;
2486 : }
2487 : }
2488 : }
2489 :
2490 : out:
2491 : /*
2492 : * Release free pages and update where the free scanner should restart,
2493 : * so we don't leave any returned pages behind in the next attempt.
2494 : */
2495 0 : if (cc->nr_freepages > 0) {
2496 0 : unsigned long free_pfn = release_freepages(&cc->freepages);
2497 :
2498 0 : cc->nr_freepages = 0;
2499 : VM_BUG_ON(free_pfn == 0);
2500 : /* The cached pfn is always the first in a pageblock */
2501 0 : free_pfn = pageblock_start_pfn(free_pfn);
2502 : /*
2503 : * Only go back, not forward. The cached pfn might have been
2504 : * already reset to zone end in compact_finished()
2505 : */
2506 0 : if (free_pfn > cc->zone->compact_cached_free_pfn)
2507 0 : cc->zone->compact_cached_free_pfn = free_pfn;
2508 : }
2509 :
2510 0 : count_compact_events(COMPACTMIGRATE_SCANNED, cc->total_migrate_scanned);
2511 0 : count_compact_events(COMPACTFREE_SCANNED, cc->total_free_scanned);
2512 :
2513 0 : trace_mm_compaction_end(cc, start_pfn, end_pfn, sync, ret);
2514 :
2515 : VM_BUG_ON(!list_empty(&cc->freepages));
2516 : VM_BUG_ON(!list_empty(&cc->migratepages));
2517 :
2518 0 : return ret;
2519 : }
2520 :
2521 0 : static enum compact_result compact_zone_order(struct zone *zone, int order,
2522 : gfp_t gfp_mask, enum compact_priority prio,
2523 : unsigned int alloc_flags, int highest_zoneidx,
2524 : struct page **capture)
2525 : {
2526 : enum compact_result ret;
2527 0 : struct compact_control cc = {
2528 : .order = order,
2529 : .search_order = order,
2530 : .gfp_mask = gfp_mask,
2531 : .zone = zone,
2532 : .mode = (prio == COMPACT_PRIO_ASYNC) ?
2533 0 : MIGRATE_ASYNC : MIGRATE_SYNC_LIGHT,
2534 : .alloc_flags = alloc_flags,
2535 : .highest_zoneidx = highest_zoneidx,
2536 : .direct_compaction = true,
2537 : .whole_zone = (prio == MIN_COMPACT_PRIORITY),
2538 0 : .ignore_skip_hint = (prio == MIN_COMPACT_PRIORITY),
2539 : .ignore_block_suitable = (prio == MIN_COMPACT_PRIORITY)
2540 : };
2541 0 : struct capture_control capc = {
2542 : .cc = &cc,
2543 : .page = NULL,
2544 : };
2545 :
2546 : /*
2547 : * Make sure the structs are really initialized before we expose the
2548 : * capture control, in case we are interrupted and the interrupt handler
2549 : * frees a page.
2550 : */
2551 0 : barrier();
2552 0 : WRITE_ONCE(current->capture_control, &capc);
2553 :
2554 0 : ret = compact_zone(&cc, &capc);
2555 :
2556 : /*
2557 : * Make sure we hide capture control first before we read the captured
2558 : * page pointer, otherwise an interrupt could free and capture a page
2559 : * and we would leak it.
2560 : */
2561 0 : WRITE_ONCE(current->capture_control, NULL);
2562 0 : *capture = READ_ONCE(capc.page);
2563 : /*
2564 : * Technically, it is also possible that compaction is skipped but
2565 : * the page is still captured out of luck(IRQ came and freed the page).
2566 : * Returning COMPACT_SUCCESS in such cases helps in properly accounting
2567 : * the COMPACT[STALL|FAIL] when compaction is skipped.
2568 : */
2569 0 : if (*capture)
2570 0 : ret = COMPACT_SUCCESS;
2571 :
2572 0 : return ret;
2573 : }
2574 :
2575 : int sysctl_extfrag_threshold = 500;
2576 :
2577 : /**
2578 : * try_to_compact_pages - Direct compact to satisfy a high-order allocation
2579 : * @gfp_mask: The GFP mask of the current allocation
2580 : * @order: The order of the current allocation
2581 : * @alloc_flags: The allocation flags of the current allocation
2582 : * @ac: The context of current allocation
2583 : * @prio: Determines how hard direct compaction should try to succeed
2584 : * @capture: Pointer to free page created by compaction will be stored here
2585 : *
2586 : * This is the main entry point for direct page compaction.
2587 : */
2588 0 : enum compact_result try_to_compact_pages(gfp_t gfp_mask, unsigned int order,
2589 : unsigned int alloc_flags, const struct alloc_context *ac,
2590 : enum compact_priority prio, struct page **capture)
2591 : {
2592 0 : int may_perform_io = (__force int)(gfp_mask & __GFP_IO);
2593 : struct zoneref *z;
2594 : struct zone *zone;
2595 0 : enum compact_result rc = COMPACT_SKIPPED;
2596 :
2597 : /*
2598 : * Check if the GFP flags allow compaction - GFP_NOIO is really
2599 : * tricky context because the migration might require IO
2600 : */
2601 0 : if (!may_perform_io)
2602 : return COMPACT_SKIPPED;
2603 :
2604 0 : trace_mm_compaction_try_to_compact_pages(order, gfp_mask, prio);
2605 :
2606 : /* Compact each zone in the list */
2607 0 : for_each_zone_zonelist_nodemask(zone, z, ac->zonelist,
2608 : ac->highest_zoneidx, ac->nodemask) {
2609 : enum compact_result status;
2610 :
2611 0 : if (prio > MIN_COMPACT_PRIORITY
2612 0 : && compaction_deferred(zone, order)) {
2613 0 : rc = max_t(enum compact_result, COMPACT_DEFERRED, rc);
2614 0 : continue;
2615 : }
2616 :
2617 0 : status = compact_zone_order(zone, order, gfp_mask, prio,
2618 0 : alloc_flags, ac->highest_zoneidx, capture);
2619 0 : rc = max(status, rc);
2620 :
2621 : /* The allocation should succeed, stop compacting */
2622 0 : if (status == COMPACT_SUCCESS) {
2623 : /*
2624 : * We think the allocation will succeed in this zone,
2625 : * but it is not certain, hence the false. The caller
2626 : * will repeat this with true if allocation indeed
2627 : * succeeds in this zone.
2628 : */
2629 0 : compaction_defer_reset(zone, order, false);
2630 :
2631 : break;
2632 : }
2633 :
2634 0 : if (prio != COMPACT_PRIO_ASYNC && (status == COMPACT_COMPLETE ||
2635 : status == COMPACT_PARTIAL_SKIPPED))
2636 : /*
2637 : * We think that allocation won't succeed in this zone
2638 : * so we defer compaction there. If it ends up
2639 : * succeeding after all, it will be reset.
2640 : */
2641 0 : defer_compaction(zone, order);
2642 :
2643 : /*
2644 : * We might have stopped compacting due to need_resched() in
2645 : * async compaction, or due to a fatal signal detected. In that
2646 : * case do not try further zones
2647 : */
2648 0 : if ((prio == COMPACT_PRIO_ASYNC && need_resched())
2649 0 : || fatal_signal_pending(current))
2650 : break;
2651 : }
2652 :
2653 : return rc;
2654 : }
2655 :
2656 : /*
2657 : * Compact all zones within a node till each zone's fragmentation score
2658 : * reaches within proactive compaction thresholds (as determined by the
2659 : * proactiveness tunable).
2660 : *
2661 : * It is possible that the function returns before reaching score targets
2662 : * due to various back-off conditions, such as, contention on per-node or
2663 : * per-zone locks.
2664 : */
2665 0 : static void proactive_compact_node(pg_data_t *pgdat)
2666 : {
2667 : int zoneid;
2668 : struct zone *zone;
2669 0 : struct compact_control cc = {
2670 : .order = -1,
2671 : .mode = MIGRATE_SYNC_LIGHT,
2672 : .ignore_skip_hint = true,
2673 : .whole_zone = true,
2674 : .gfp_mask = GFP_KERNEL,
2675 : .proactive_compaction = true,
2676 : };
2677 :
2678 0 : for (zoneid = 0; zoneid < MAX_NR_ZONES; zoneid++) {
2679 0 : zone = &pgdat->node_zones[zoneid];
2680 0 : if (!populated_zone(zone))
2681 0 : continue;
2682 :
2683 0 : cc.zone = zone;
2684 :
2685 0 : compact_zone(&cc, NULL);
2686 :
2687 0 : count_compact_events(KCOMPACTD_MIGRATE_SCANNED,
2688 0 : cc.total_migrate_scanned);
2689 0 : count_compact_events(KCOMPACTD_FREE_SCANNED,
2690 0 : cc.total_free_scanned);
2691 : }
2692 0 : }
2693 :
2694 : /* Compact all zones within a node */
2695 0 : static void compact_node(int nid)
2696 : {
2697 0 : pg_data_t *pgdat = NODE_DATA(nid);
2698 : int zoneid;
2699 : struct zone *zone;
2700 0 : struct compact_control cc = {
2701 : .order = -1,
2702 : .mode = MIGRATE_SYNC,
2703 : .ignore_skip_hint = true,
2704 : .whole_zone = true,
2705 : .gfp_mask = GFP_KERNEL,
2706 : };
2707 :
2708 :
2709 0 : for (zoneid = 0; zoneid < MAX_NR_ZONES; zoneid++) {
2710 :
2711 0 : zone = &pgdat->node_zones[zoneid];
2712 0 : if (!populated_zone(zone))
2713 0 : continue;
2714 :
2715 0 : cc.zone = zone;
2716 :
2717 0 : compact_zone(&cc, NULL);
2718 : }
2719 0 : }
2720 :
2721 : /* Compact all nodes in the system */
2722 : static void compact_nodes(void)
2723 : {
2724 : int nid;
2725 :
2726 : /* Flush pending updates to the LRU lists */
2727 0 : lru_add_drain_all();
2728 :
2729 0 : for_each_online_node(nid)
2730 0 : compact_node(nid);
2731 : }
2732 :
2733 : /*
2734 : * Tunable for proactive compaction. It determines how
2735 : * aggressively the kernel should compact memory in the
2736 : * background. It takes values in the range [0, 100].
2737 : */
2738 : unsigned int __read_mostly sysctl_compaction_proactiveness = 20;
2739 :
2740 0 : int compaction_proactiveness_sysctl_handler(struct ctl_table *table, int write,
2741 : void *buffer, size_t *length, loff_t *ppos)
2742 : {
2743 : int rc, nid;
2744 :
2745 0 : rc = proc_dointvec_minmax(table, write, buffer, length, ppos);
2746 0 : if (rc)
2747 : return rc;
2748 :
2749 0 : if (write && sysctl_compaction_proactiveness) {
2750 0 : for_each_online_node(nid) {
2751 0 : pg_data_t *pgdat = NODE_DATA(nid);
2752 :
2753 0 : if (pgdat->proactive_compact_trigger)
2754 0 : continue;
2755 :
2756 0 : pgdat->proactive_compact_trigger = true;
2757 0 : trace_mm_compaction_wakeup_kcompactd(pgdat->node_id, -1,
2758 0 : pgdat->nr_zones - 1);
2759 0 : wake_up_interruptible(&pgdat->kcompactd_wait);
2760 : }
2761 : }
2762 :
2763 : return 0;
2764 : }
2765 :
2766 : /*
2767 : * This is the entry point for compacting all nodes via
2768 : * /proc/sys/vm/compact_memory
2769 : */
2770 0 : int sysctl_compaction_handler(struct ctl_table *table, int write,
2771 : void *buffer, size_t *length, loff_t *ppos)
2772 : {
2773 0 : if (write)
2774 : compact_nodes();
2775 :
2776 0 : return 0;
2777 : }
2778 :
2779 : #if defined(CONFIG_SYSFS) && defined(CONFIG_NUMA)
2780 : static ssize_t compact_store(struct device *dev,
2781 : struct device_attribute *attr,
2782 : const char *buf, size_t count)
2783 : {
2784 : int nid = dev->id;
2785 :
2786 : if (nid >= 0 && nid < nr_node_ids && node_online(nid)) {
2787 : /* Flush pending updates to the LRU lists */
2788 : lru_add_drain_all();
2789 :
2790 : compact_node(nid);
2791 : }
2792 :
2793 : return count;
2794 : }
2795 : static DEVICE_ATTR_WO(compact);
2796 :
2797 : int compaction_register_node(struct node *node)
2798 : {
2799 : return device_create_file(&node->dev, &dev_attr_compact);
2800 : }
2801 :
2802 : void compaction_unregister_node(struct node *node)
2803 : {
2804 : return device_remove_file(&node->dev, &dev_attr_compact);
2805 : }
2806 : #endif /* CONFIG_SYSFS && CONFIG_NUMA */
2807 :
2808 : static inline bool kcompactd_work_requested(pg_data_t *pgdat)
2809 : {
2810 310 : return pgdat->kcompactd_max_order > 0 || kthread_should_stop() ||
2811 155 : pgdat->proactive_compact_trigger;
2812 : }
2813 :
2814 0 : static bool kcompactd_node_suitable(pg_data_t *pgdat)
2815 : {
2816 : int zoneid;
2817 : struct zone *zone;
2818 0 : enum zone_type highest_zoneidx = pgdat->kcompactd_highest_zoneidx;
2819 :
2820 0 : for (zoneid = 0; zoneid <= highest_zoneidx; zoneid++) {
2821 0 : zone = &pgdat->node_zones[zoneid];
2822 :
2823 0 : if (!populated_zone(zone))
2824 0 : continue;
2825 :
2826 0 : if (compaction_suitable(zone, pgdat->kcompactd_max_order, 0,
2827 : highest_zoneidx) == COMPACT_CONTINUE)
2828 : return true;
2829 : }
2830 :
2831 : return false;
2832 : }
2833 :
2834 0 : static void kcompactd_do_work(pg_data_t *pgdat)
2835 : {
2836 : /*
2837 : * With no special task, compact all zones so that a page of requested
2838 : * order is allocatable.
2839 : */
2840 : int zoneid;
2841 : struct zone *zone;
2842 0 : struct compact_control cc = {
2843 : .order = pgdat->kcompactd_max_order,
2844 0 : .search_order = pgdat->kcompactd_max_order,
2845 0 : .highest_zoneidx = pgdat->kcompactd_highest_zoneidx,
2846 : .mode = MIGRATE_SYNC_LIGHT,
2847 : .ignore_skip_hint = false,
2848 : .gfp_mask = GFP_KERNEL,
2849 : };
2850 0 : trace_mm_compaction_kcompactd_wake(pgdat->node_id, cc.order,
2851 : cc.highest_zoneidx);
2852 0 : count_compact_event(KCOMPACTD_WAKE);
2853 :
2854 0 : for (zoneid = 0; zoneid <= cc.highest_zoneidx; zoneid++) {
2855 : int status;
2856 :
2857 0 : zone = &pgdat->node_zones[zoneid];
2858 0 : if (!populated_zone(zone))
2859 0 : continue;
2860 :
2861 0 : if (compaction_deferred(zone, cc.order))
2862 0 : continue;
2863 :
2864 0 : if (compaction_suitable(zone, cc.order, 0, zoneid) !=
2865 : COMPACT_CONTINUE)
2866 0 : continue;
2867 :
2868 0 : if (kthread_should_stop())
2869 0 : return;
2870 :
2871 0 : cc.zone = zone;
2872 0 : status = compact_zone(&cc, NULL);
2873 :
2874 0 : if (status == COMPACT_SUCCESS) {
2875 0 : compaction_defer_reset(zone, cc.order, false);
2876 0 : } else if (status == COMPACT_PARTIAL_SKIPPED || status == COMPACT_COMPLETE) {
2877 : /*
2878 : * Buddy pages may become stranded on pcps that could
2879 : * otherwise coalesce on the zone's free area for
2880 : * order >= cc.order. This is ratelimited by the
2881 : * upcoming deferral.
2882 : */
2883 0 : drain_all_pages(zone);
2884 :
2885 : /*
2886 : * We use sync migration mode here, so we defer like
2887 : * sync direct compaction does.
2888 : */
2889 0 : defer_compaction(zone, cc.order);
2890 : }
2891 :
2892 0 : count_compact_events(KCOMPACTD_MIGRATE_SCANNED,
2893 0 : cc.total_migrate_scanned);
2894 0 : count_compact_events(KCOMPACTD_FREE_SCANNED,
2895 0 : cc.total_free_scanned);
2896 : }
2897 :
2898 : /*
2899 : * Regardless of success, we are done until woken up next. But remember
2900 : * the requested order/highest_zoneidx in case it was higher/tighter
2901 : * than our current ones
2902 : */
2903 0 : if (pgdat->kcompactd_max_order <= cc.order)
2904 0 : pgdat->kcompactd_max_order = 0;
2905 0 : if (pgdat->kcompactd_highest_zoneidx >= cc.highest_zoneidx)
2906 0 : pgdat->kcompactd_highest_zoneidx = pgdat->nr_zones - 1;
2907 : }
2908 :
2909 1 : void wakeup_kcompactd(pg_data_t *pgdat, int order, int highest_zoneidx)
2910 : {
2911 1 : if (!order)
2912 : return;
2913 :
2914 0 : if (pgdat->kcompactd_max_order < order)
2915 0 : pgdat->kcompactd_max_order = order;
2916 :
2917 0 : if (pgdat->kcompactd_highest_zoneidx > highest_zoneidx)
2918 0 : pgdat->kcompactd_highest_zoneidx = highest_zoneidx;
2919 :
2920 : /*
2921 : * Pairs with implicit barrier in wait_event_freezable()
2922 : * such that wakeups are not missed.
2923 : */
2924 0 : if (!wq_has_sleeper(&pgdat->kcompactd_wait))
2925 : return;
2926 :
2927 0 : if (!kcompactd_node_suitable(pgdat))
2928 : return;
2929 :
2930 0 : trace_mm_compaction_wakeup_kcompactd(pgdat->node_id, order,
2931 : highest_zoneidx);
2932 0 : wake_up_interruptible(&pgdat->kcompactd_wait);
2933 : }
2934 :
2935 : /*
2936 : * The background compaction daemon, started as a kernel thread
2937 : * from the init process.
2938 : */
2939 1 : static int kcompactd(void *p)
2940 : {
2941 1 : pg_data_t *pgdat = (pg_data_t *)p;
2942 1 : struct task_struct *tsk = current;
2943 1 : long default_timeout = msecs_to_jiffies(HPAGE_FRAG_CHECK_INTERVAL_MSEC);
2944 1 : long timeout = default_timeout;
2945 :
2946 1 : const struct cpumask *cpumask = cpumask_of_node(pgdat->node_id);
2947 :
2948 1 : if (!cpumask_empty(cpumask))
2949 1 : set_cpus_allowed_ptr(tsk, cpumask);
2950 :
2951 1 : set_freezable();
2952 :
2953 1 : pgdat->kcompactd_max_order = 0;
2954 1 : pgdat->kcompactd_highest_zoneidx = pgdat->nr_zones - 1;
2955 :
2956 53 : while (!kthread_should_stop()) {
2957 : unsigned long pflags;
2958 :
2959 : /*
2960 : * Avoid the unnecessary wakeup for proactive compaction
2961 : * when it is disabled.
2962 : */
2963 52 : if (!sysctl_compaction_proactiveness)
2964 0 : timeout = MAX_SCHEDULE_TIMEOUT;
2965 52 : trace_mm_compaction_kcompactd_sleep(pgdat->node_id);
2966 207 : if (wait_event_freezable_timeout(pgdat->kcompactd_wait,
2967 0 : kcompactd_work_requested(pgdat), timeout) &&
2968 0 : !pgdat->proactive_compact_trigger) {
2969 :
2970 0 : psi_memstall_enter(&pflags);
2971 0 : kcompactd_do_work(pgdat);
2972 0 : psi_memstall_leave(&pflags);
2973 : /*
2974 : * Reset the timeout value. The defer timeout from
2975 : * proactive compaction is lost here but that is fine
2976 : * as the condition of the zone changing substantionally
2977 : * then carrying on with the previous defer interval is
2978 : * not useful.
2979 : */
2980 0 : timeout = default_timeout;
2981 0 : continue;
2982 : }
2983 :
2984 : /*
2985 : * Start the proactive work with default timeout. Based
2986 : * on the fragmentation score, this timeout is updated.
2987 : */
2988 51 : timeout = default_timeout;
2989 51 : if (should_proactive_compact_node(pgdat)) {
2990 : unsigned int prev_score, score;
2991 :
2992 0 : prev_score = fragmentation_score_node(pgdat);
2993 0 : proactive_compact_node(pgdat);
2994 0 : score = fragmentation_score_node(pgdat);
2995 : /*
2996 : * Defer proactive compaction if the fragmentation
2997 : * score did not go down i.e. no progress made.
2998 : */
2999 0 : if (unlikely(score >= prev_score))
3000 0 : timeout =
3001 : default_timeout << COMPACT_MAX_DEFER_SHIFT;
3002 : }
3003 51 : if (unlikely(pgdat->proactive_compact_trigger))
3004 0 : pgdat->proactive_compact_trigger = false;
3005 : }
3006 :
3007 0 : return 0;
3008 : }
3009 :
3010 : /*
3011 : * This kcompactd start function will be called by init and node-hot-add.
3012 : * On node-hot-add, kcompactd will moved to proper cpus if cpus are hot-added.
3013 : */
3014 1 : void kcompactd_run(int nid)
3015 : {
3016 1 : pg_data_t *pgdat = NODE_DATA(nid);
3017 :
3018 1 : if (pgdat->kcompactd)
3019 : return;
3020 :
3021 2 : pgdat->kcompactd = kthread_run(kcompactd, pgdat, "kcompactd%d", nid);
3022 1 : if (IS_ERR(pgdat->kcompactd)) {
3023 0 : pr_err("Failed to start kcompactd on node %d\n", nid);
3024 0 : pgdat->kcompactd = NULL;
3025 : }
3026 : }
3027 :
3028 : /*
3029 : * Called by memory hotplug when all memory in a node is offlined. Caller must
3030 : * be holding mem_hotplug_begin/done().
3031 : */
3032 0 : void kcompactd_stop(int nid)
3033 : {
3034 0 : struct task_struct *kcompactd = NODE_DATA(nid)->kcompactd;
3035 :
3036 0 : if (kcompactd) {
3037 0 : kthread_stop(kcompactd);
3038 0 : NODE_DATA(nid)->kcompactd = NULL;
3039 : }
3040 0 : }
3041 :
3042 : /*
3043 : * It's optimal to keep kcompactd on the same CPUs as their memory, but
3044 : * not required for correctness. So if the last cpu in a node goes
3045 : * away, we get changed to run anywhere: as the first one comes back,
3046 : * restore their cpu bindings.
3047 : */
3048 0 : static int kcompactd_cpu_online(unsigned int cpu)
3049 : {
3050 : int nid;
3051 :
3052 0 : for_each_node_state(nid, N_MEMORY) {
3053 0 : pg_data_t *pgdat = NODE_DATA(nid);
3054 : const struct cpumask *mask;
3055 :
3056 0 : mask = cpumask_of_node(pgdat->node_id);
3057 :
3058 0 : if (cpumask_any_and(cpu_online_mask, mask) < nr_cpu_ids)
3059 : /* One of our CPUs online: restore mask */
3060 0 : if (pgdat->kcompactd)
3061 0 : set_cpus_allowed_ptr(pgdat->kcompactd, mask);
3062 : }
3063 0 : return 0;
3064 : }
3065 :
3066 1 : static int __init kcompactd_init(void)
3067 : {
3068 : int nid;
3069 : int ret;
3070 :
3071 1 : ret = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN,
3072 : "mm/compaction:online",
3073 : kcompactd_cpu_online, NULL);
3074 1 : if (ret < 0) {
3075 0 : pr_err("kcompactd: failed to register hotplug callbacks.\n");
3076 0 : return ret;
3077 : }
3078 :
3079 1 : for_each_node_state(nid, N_MEMORY)
3080 1 : kcompactd_run(nid);
3081 : return 0;
3082 : }
3083 : subsys_initcall(kcompactd_init)
3084 :
3085 : #endif /* CONFIG_COMPACTION */
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